WIP: Retrieve merge request status for any job

[derrickgw]

This merge request adds a pipeline function gitlabMergeRequestStatus(projectId, branchName) to retrieve merge request information about any given project/branch.

This would be useful in cases where the pipeline needs to behave differently if there is a merge request open, e.g. running long resource intensive tests only for merge requests, or in pipelines that are triggered by other jobs. This is a partial solution to the fact that Multi-branch pipelines don't get run for merge requests. These values are retrieved directly since they can't be propagated to the multi-branch build.

Ideally this could be tested by having a mock gitlab instance provide canned JSON responses, but I don't know how to accomplish that within the existing framework.

This is WIP to:

• Gauge interest
• Get code review
• Get advice on how to test

[markjacksonfishing]

@derrickgw did you run a mvn clean install?