Create layer to integrate with Jira development panel (presenting commits)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

Development

• Respond to OAuth flow on behalf of Github
• Adjust the request to our V3 API with the correct Authorization header format (middleware)
• Hardcode github commits fetching layer (make sure what data is really necessary)
• Replace hardcoded API code with proper entities
• Find a solution to Jira working with the relative url /jira when linking commits, repository, etc
• Make it work for groups
• Add premium license check
• Support file diffs

What are the relevant issue numbers?

Closes #2381 (closed)