Add "bypassed" field to merge request API
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## Problem to Solve
When a merge request which has changes requested has been `bypassed` there's currently no way to see that information via the API.
## Proposal
We should add a new field to the API that tells you if a merge request has been bypassed. We could add this on the [`get single MR`](https://docs.gitlab.com/ee/api/merge_requests.html#get-single-mr) endpoint.
issue