🎨 style: change `http/https` header word/sentence casing (#555)

Currently all HTTP request headers are in snake case and upper case.
The adopted standard is kebab case and title case.

Here you will find more details:
https://en.wikipedia.org/wiki/List_of_HTTP_header_fields#Standard_request_fields

src/engines/bing.rs

@@ -79,13 +79,13 @@ impl SearchEngine for Bing {
         }
 
         let header_map = HeaderMap::try_from(&HashMap::from([
-            ("USER_AGENT".to_string(), user_agent.to_string()),
-            ("REFERER".to_string(), "https://google.com/".to_string()),
+            ("User-Agent".to_string(), user_agent.to_string()),
+            ("Referer".to_string(), "https://google.com/".to_string()),
             (
-                "CONTENT_TYPE".to_string(),
+                "Content-Type".to_string(),
                 "application/x-www-form-urlencoded".to_string(),
             ),
-            ("COOKIE".to_string(), cookie_string),
+            ("Cookie".to_string(), cookie_string),
         ]))
         .change_context(EngineError::UnexpectedError)?;
 

src/engines/brave.rs

@@ -54,14 +54,14 @@ impl SearchEngine for Brave {
         };
 
         let header_map = HeaderMap::try_from(&HashMap::from([
-            ("USER_AGENT".to_string(), user_agent.to_string()),
+            ("User-Agent".to_string(), user_agent.to_string()),
             (
-                "CONTENT_TYPE".to_string(),
+                "Content-Type".to_string(),
                 "application/x-www-form-urlencoded".to_string(),
             ),
-            ("REFERER".to_string(), "https://google.com/".to_string()),
+            ("Referer".to_string(), "https://google.com/".to_string()),
             (
-                "COOKIE".to_string(),
+                "Cookie".to_string(),
                 format!("safe_search={safe_search_level}"),
             ),
         ]))

src/engines/duckduckgo.rs

@@ -65,13 +65,13 @@ impl SearchEngine for DuckDuckGo {
 
         // initializing HeaderMap and adding appropriate headers.
         let header_map = HeaderMap::try_from(&HashMap::from([
-            ("USER_AGENT".to_string(), user_agent.to_string()),
-            ("REFERER".to_string(), "https://google.com/".to_string()),
+            ("User-Agent".to_string(), user_agent.to_string()),
+            ("Referer".to_string(), "https://google.com/".to_string()),
             (
-                "CONTENT_TYPE".to_string(),
+                "Content-Type".to_string(),
                 "application/x-www-form-urlencoded".to_string(),
             ),
-            ("COOKIE".to_string(), "kl=wt-wt".to_string()),
+            ("Cookie".to_string(), "kl=wt-wt".to_string()),
         ]))
         .change_context(EngineError::UnexpectedError)?;
 

src/engines/librex.rs

@@ -72,11 +72,11 @@ impl SearchEngine for LibreX {
 
         // initializing HeaderMap and adding appropriate headers.
         let header_map = HeaderMap::try_from(&HashMap::from([
-            ("USER_AGENT".to_string(), user_agent.to_string()),
-            ("REFERER".to_string(), "https://google.com/".to_string()),
-            ("CONTENT_TYPE".to_string(), "application/x-www-form-urlencoded".to_string()),
+            ("User-Agent".to_string(), user_agent.to_string()),
+            ("Referer".to_string(), "https://google.com/".to_string()),
+            ("Content-Type".to_string(), "application/x-www-form-urlencoded".to_string()),
             (
-                "COOKIE".to_string(),
+                "Cookie".to_string(),
                 "theme=amoled; disable_special=on; disable_frontends=on; language=en; number_of_results=10; safe_search=on; save=1".to_string(),
             ),
         ]))

src/engines/mojeek.rs

@@ -129,13 +129,13 @@ impl SearchEngine for Mojeek {
         }
 
         let header_map = HeaderMap::try_from(&HashMap::from([
-            ("USER_AGENT".to_string(), user_agent.to_string()),
-            ("REFERER".to_string(), "https://google.com/".to_string()),
+            ("User-Agent".to_string(), user_agent.to_string()),
+            ("Referer".to_string(), "https://google.com/".to_string()),
             (
-                "CONTENT_TYPE".to_string(),
+                "Content-Type".to_string(),
                 "application/x-www-form-urlencoded".to_string(),
             ),
-            ("COOKIE".to_string(), cookie_string),
+            ("Cookie".to_string(), cookie_string),
         ]))
         .change_context(EngineError::UnexpectedError)?;
 

src/engines/searx.rs

@@ -66,10 +66,10 @@ impl SearchEngine for Searx {
 
         // initializing headers and adding appropriate headers.
         let header_map = HeaderMap::try_from(&HashMap::from([
-            ("USER_AGENT".to_string(), user_agent.to_string()),
-            ("REFERER".to_string(), "https://google.com/".to_string()),
-            ("CONTENT_TYPE".to_string(), "application/x-www-form-urlencoded".to_string()),
-            ("COOKIE".to_string(), "categories=general; language=auto; locale=en; autocomplete=duckduckgo; image_proxy=1; method=POST; safesearch=2; theme=simple; results_on_new_tab=1; doi_resolver=oadoi.org; simple_style=auto; center_alignment=1; query_in_title=1; infinite_scroll=0; disabled_engines=; enabled_engines=\"archive is__general\\054yep__general\\054curlie__general\\054currency__general\\054ddg definitions__general\\054wikidata__general\\054duckduckgo__general\\054tineye__general\\054lingva__general\\054startpage__general\\054yahoo__general\\054wiby__general\\054marginalia__general\\054alexandria__general\\054wikibooks__general\\054wikiquote__general\\054wikisource__general\\054wikiversity__general\\054wikivoyage__general\\054dictzone__general\\054seznam__general\\054mojeek__general\\054naver__general\\054wikimini__general\\054brave__general\\054petalsearch__general\\054goo__general\"; disabled_plugins=; enabled_plugins=\"searx.plugins.hostname_replace\\054searx.plugins.oa_doi_rewrite\\054searx.plugins.vim_hotkeys\"; tokens=; maintab=on; enginetab=on".to_string())
+            ("User-Agent".to_string(), user_agent.to_string()),
+            ("Referer".to_string(), "https://google.com/".to_string()),
+            ("Content-Type".to_string(), "application/x-www-form-urlencoded".to_string()),
+            ("Cookie".to_string(), "categories=general; language=auto; locale=en; autocomplete=duckduckgo; image_proxy=1; method=POST; safesearch=2; theme=simple; results_on_new_tab=1; doi_resolver=oadoi.org; simple_style=auto; center_alignment=1; query_in_title=1; infinite_scroll=0; disabled_engines=; enabled_engines=\"archive is__general\\054yep__general\\054curlie__general\\054currency__general\\054ddg definitions__general\\054wikidata__general\\054duckduckgo__general\\054tineye__general\\054lingva__general\\054startpage__general\\054yahoo__general\\054wiby__general\\054marginalia__general\\054alexandria__general\\054wikibooks__general\\054wikiquote__general\\054wikisource__general\\054wikiversity__general\\054wikivoyage__general\\054dictzone__general\\054seznam__general\\054mojeek__general\\054naver__general\\054wikimini__general\\054brave__general\\054petalsearch__general\\054goo__general\"; disabled_plugins=; enabled_plugins=\"searx.plugins.hostname_replace\\054searx.plugins.oa_doi_rewrite\\054searx.plugins.vim_hotkeys\"; tokens=; maintab=on; enginetab=on".to_string())
         ]))
         .change_context(EngineError::UnexpectedError)?;
 

src/engines/startpage.rs

@@ -57,13 +57,13 @@ impl SearchEngine for Startpage {
 
         // initializing HeaderMap and adding appropriate headers.
         let header_map = HeaderMap::try_from(&HashMap::from([
-            ("USER_AGENT".to_string(), user_agent.to_string()),
-            ("REFERER".to_string(), "https://google.com/".to_string()),
+            ("User-Agent".to_string(), user_agent.to_string()),
+            ("Referer".to_string(), "https://google.com/".to_string()),
             (
-                "CONTENT_TYPE".to_string(),
+                "Content-Type".to_string(),
                 "application/x-www-form-urlencoded".to_string(),
             ),
-            ("COOKIE".to_string(), "preferences=connect_to_serverEEE0N1Ndate_timeEEEworldN1Ndisable_family_filterEEE0N1Ndisable_open_in_new_windowEEE0N1Nenable_post_methodEEE1N1Nenable_proxy_safety_suggestEEE1N1Nenable_stay_controlEEE0N1Ninstant_answersEEE1N1Nlang_homepageEEEs%2Fnight%2FenN1NlanguageEEEenglishN1Nlanguage_uiEEEenglishN1Nnum_of_resultsEEE10N1Nsearch_results_regionEEEallN1NsuggestionsEEE1N1Nwt_unitEEEcelsius".to_string()),
+            ("Cookie".to_string(), "preferences=connect_to_serverEEE0N1Ndate_timeEEEworldN1Ndisable_family_filterEEE0N1Ndisable_open_in_new_windowEEE0N1Nenable_post_methodEEE1N1Nenable_proxy_safety_suggestEEE1N1Nenable_stay_controlEEE0N1Ninstant_answersEEE1N1Nlang_homepageEEEs%2Fnight%2FenN1NlanguageEEEenglishN1Nlanguage_uiEEEenglishN1Nnum_of_resultsEEE10N1Nsearch_results_regionEEEallN1NsuggestionsEEE1N1Nwt_unitEEEcelsius".to_string()),
         ]))
         .change_context(EngineError::UnexpectedError)?;