Create a service method to fetch the merge request approvals done by one user

Summary

Call the GitLab API to retrieve all the merge request approvals a user has made within a certain time stamp.

Checklist

• retrieve all the merge requests in one project that a user has approved
• retrieve all merge requests in a group that a user has approved

Implementation details

Potential APIs that the information can be retrieved from:

• GitLab Events API
• GitLab Merge Requests API