Refactor/tests

[Blackglade]

For most tests, metrumresearchgroup/rbabylon library was used.

The following tests however used the metrumresearchgroup/pkgr library:

• Conventional Commits Parsing on Pull Request
• Project Boards test suite

As of my last update, the following functions don't have tests:

• ~sanitize_response()~
• ~get_milestones()~
• get_token()
• ~graphql_query()~
• create_labels()
• delete_all_labels()
• ~get_query_results()~
• add_pull_request_reviewers()
• create_pull_request()
• create_projectboard()
• clone_projectboard()
• ~get_user_info()~
• assign_to_object()
• %||%

Note: not all of these functions may need tests. These simple functions are BOLDED