Adds cookie auth support to ApiKeyAuth in dart2 templates

Created by: tek08

Issue #7344

This modifies api_client.mustache and api_key_auth.mustache to allow an option of cookie for location of apiKey. To test, you can create a security schema such as:

securitySchemes:
  ExampleCookieAuth:
    type: apiKey
    in: cookie
    name: session

This should send a Cookie header up to server with semi-colon separated auth keys/values e.g.:

Cookie: session=12345; otherAuthKey=abcdef

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• If contributing template-only or documentation-only changes which will change sample output, build the project beforehand.
• Run the shell script ./bin/generate-samples.shto update all Petstore samples related to your fix. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. For Windows users, please run the script in Git BASH.
• File the PR against the correct branch: master
• Copy the technical committee to review the pull request if your PR is targeting a particular programming language. (@ircecho @swipesight @jaumard @athornz @amondnet )

modules/openapi-generator/src/main/resources/dart2/auth/api_key_auth.mustache

@@ -24,6 +24,10 @@ class ApiKeyAuth implements Authentication {
       queryParams.add(QueryParam(paramName, value));
     } else if (location == 'header' && value != null) {
       headerParams[paramName] = value;
+    } else if (location == 'cookie' && value != null) {
+      headerParams.update('Cookie', (String existingCookie) {
+        return "$existingCookie; $paramName=$value";
+      }, ifAbsent: () => '$paramName=$value');
     }
   }
 }

modules/openapi-generator/src/main/resources/dart2/api_client.mustache

@@ -31,7 +31,7 @@ class ApiClient {
   {{/isBasicBearer}}
   {{/isBasic}}
   {{#isApiKey}}
-    _authentications['{{name}}'] = ApiKeyAuth({{#isKeyInHeader}}"header"{{/isKeyInHeader}}{{^isKeyInHeader}}"query"{{/isKeyInHeader}}, "{{keyParamName}}");
+    _authentications['{{name}}'] = ApiKeyAuth({{#isKeyInCookie}}"cookie"{{/isKeyInCookie}}{{^isKeyInCookie}}{{#isKeyInHeader}}"header"{{/isKeyInHeader}}{{^isKeyInHeader}}"query"{{/isKeyInHeader}}{{/isKeyInCookie}}, "{{keyParamName}}");
   {{/isApiKey}}
   {{#isOAuth}}
     _authentications['{{name}}'] = OAuth();

samples/client/petstore/dart2/petstore_client_lib/lib/auth/api_key_auth.dart

@@ -24,6 +24,10 @@ class ApiKeyAuth implements Authentication {
       queryParams.add(QueryParam(paramName, value));
     } else if (location == 'header' && value != null) {
       headerParams[paramName] = value;
+    } else if (location == 'cookie' && value != null) {
+      headerParams.update('Cookie', (String existingCookie) {
+        return "$existingCookie; $paramName=$value";
+      }, ifAbsent: () => '$paramName=$value');
     }
   }
 }