Write tests for GitHub.Sync.pull_request_event/1

[begedin]

Problem

GitHub.Sync.pull_request_event/1 is currently completely untested. Since we want to unit test it's individual elements to, it should suffice to test each possible outcome of the transaction performed by the tests, as defined by GitHub.Sync.pull_request_event_outcome()

Subtasks

• write test for {:ok, map} outcome
• write test for {:error, :repo_not_found} outcome
• write test for {:error, :fetching_issue, struct} outcome
• write test for {:error, :validating_github_pull_request, Changeset.t()} outcome
• write test for {:error, :validating_github_issue, Changeset.t()} outcome
• write test for {:error, :validating_user, Changeset.t()} outcome
• write test for {:error, :multiple_issue_users_match} outcome
• write test for {:error, :validating_task, Changeset.t()} outcome
• write test for {:error, :unexpected_transaction_outcome, any} outcome

[vishaldeepak]

@begedin Any major changes coming up to this or should i start working? Talking with reference similar to this #1374 (comment)

[begedin]

@vishaldeepak Same as #1374, I would recommend branching off of #1370 and then submitting a PR against that onne. Once #1370 is merged, we can then rebase onto develop.

[zacck-zz]

Going to jump on this one since its still up for grabs ...