Add pagination support to GitHub.API.Installation.repositories

[joshsmith]

What's in this PR?

Adds pagination support to GitHub.API.Installation.repositories.

Wasn't sure if a test was necessary given that it was failing until I got it working. Don't think we need to do extra testing for this to be paginating.

Any thoughts here?

References

Fixes #1108

[joshsmith]

It looks like this is erroring due to the fact that get_all may not handle individual errors from the GitHub API well.

For example, the list returned seems to be:

[%CodeCorps.GitHub.APIError{documentation_url: nil, errors: nil,
  message: "{\"message\":\"Maximum number of login attempts exceeded. Please try again later.\",\"documentation_url\":\"https://developer.github.com/v3\"}",
  status_code: 404}]

And Installation.repositories does not indicate that this is an error, but instead tries to pass this off as a list of repos.

[begedin]

@joshsmith Took me a bit to get here, but I managed to write some behavior which should allow us to more easily recover from various potential issues during a paginated request.

There were a bunch of inconsistencies that needed fixing, as well as miscellaneous minor corrections I had to do to get to that point, but overall, this should increase stability.

Just as a minor tip, I found that looking at dialyzer errors, which we have quite a lot of, using mix dialyzer was helpful in identifying potential bugs. We should strive to resolve as much of those as we can and keep them to a minimum, but I don't think it should be our focus. Just something we do while we work on a feature or bug.

The commit message should clarify what I did but I'll also copy it here for convenience

• added API.Errors namespace, to move other errors into
• added API.Errors.PaginationError
• rewrote some specs that were breaking contracts
• standardized get_all/3 response to match request/5 response ({:ok, data} or {:error, error})
• corrected several type definitions
• added support for recovering from failed individual page requests during get_all/3
• added support for recovering from failed initial head request during get_all/3
• added support for marshalling a failed and successful head response (body is ""so poison was failing to decode)
• rewrote ResultAggregator docs and argument names so they reflect the fact that it can be used for aggregating any standard response list, not just db commit
• wrote tests to cover new behaviors

[joshsmith]

This looks great to me. I can't approve since it's my PR, but will rebase and merge now. Great work!