Start consolodating Github REST API URLs into a central place

[MoralCode]

Description
This takes inspiration from the discussion in #3597 and is a step towards resolving #3277

This pr:

• refactors a few commonly reused functions that generate github API URLs (specifically for the issues, contributors, and user endpoints) so that the url building happens within the existing GithubDataAccess class.
• creates a function that brings the fetching of github user API data into this class as well (a model for future plans for the other endpoints)
• creates a user_endpoint_urls function that, given a username, can recreate the urls that the github API responds with. This change compliments Remove API url columns (that can be recalculated) from the contributors table #3747.
• creates a currently-unused general-purpose function to generate URLs for querying Github's search API, removing the need to manually assemble the URL in an API-compliant way from clients that use it. clients just provide the query string as it would be typed into githubs search box. This change also enabled some current legacy facade code for doing these searches to be replaced with this general-purpose implementation.

Notes for Reviewers
Augur collection appears to run smoothly with this PR on my local dev instance, indicating this change doesnt cause breakage.

Signed commits

• Yes, I signed my commits.

[shlokgilda]

Like the idea.

One thing that needs fixing before merge: there's an operator precedence bug in issues_endpoint_url that'll break the trailing_slash=False path. Python evaluates the ternary after the +, so when trailing_slash=False you get an empty string back instead of the URL without a slash. The issues endpoint actually hits this path, so it'd break issue collection.

Also, _base_url() is defined but never called. issues_endpoint_url still hardcodes the domain. Worth wiring that in since that's the whole point of the refactor.

Details in the inline comments.

[shlokgilda]

LGTM

[sgoggins]

Needs to be tested before merge.

[github-actions]

[pylint] _{reported by reviewdog 🐶}
E0602: Undefined variable 'repo' (undefined-variable)

[MoralCode]

this commit shouldnt be here....

[MoralCode]

currently testing on my dev instance