Preparation and refactoring for creating releases

[sleberknight]

This commit refactors existing code and does some preparation work to make creating new releases easier. Mostly this involves adding a 'post' method to GithubApi and refactoring common GitHub request and response processing code.

Details:

• Refactor GithubApi by extracting common GitHub REST API code, renaming Response to GitHubResponse and adding more properties, and adding a new #post method.
• Add a companion object to GitHubResponse to allow easy creation from an HttpResponse.
• Add several extension methods for HttpHeaders in HttpHeadersExtensions.kt.
• Add response check to GithubListFetcher, since the GithubApi no longer throws an exception when it gets an unsuccessful status code.

Related to #33

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
98.1% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud