Use new issuetracker api

[sdorra]

Proposed changes

Use new issuetracker api to support pull requests and comments.

Your checklist for this pull request

• [X] PR is well described and the description can be used as commit message on squash
• [X] Related issues linked to PR if existing and labels set
• [X] Target branch is not master (in most cases develop should bet the target of choice)
• [X] Code does not conflict with target branch
• [X] New code is covered with unit tests
• [X] Changelog entry file created in gradle/changelog
• [X] Definition of Done's fulfilled: DoD // UI DoD
• [X] Documentation updated (only necessary for new features or changed behaviour)

Checklist for branch merge request (not required for forks)

• [x] Branch is green/blue on Jenkins
• [ ] Quality Gate passed on SonarQube