Iss #139 - Change when validation happens for GH status UI endpoint

Previously, validation happened on every call to this endpoint. That led to issues with some of our calls where things were being revalidated when it wasn't needed. This would lead to failures to display, when the data should be able to be presented as is.

Additionally, refactoring was done to split the validation status calls to a separate service to keep the code cleaner and more legible.

requested review from @zacharysabourin and @cguindon

@cguindon I added 2 failure points for the GH status call:

• When the project doesn't have a visible installation !154 (diffs)
• When the PR is in a non-open state !154 (diffs)

We had talked about these, and I just wanted to confirm that they were added, especially the first one.

approved this merge request

mentioned in commit 27b40365

merged