Chain of Trust on Github: Migrate to the v4 API

[JohanLorenzo]

We're using the v3 API, because that was the one officially supported at the time.

This led us (for instance) to use this non-API call:

scriptworker/scriptworker/github.py

Lines 102 to 132 in 053e76b

	async def has_commit_landed_on_repository(self, context, revision):
	"""Tell if a commit was landed on the repository or if it just comes from a pull request.
	Args:
	context (scriptworker.context.Context): the scriptworker context.
	revision (str): the commit hash or the tag name.
	Returns:
	bool: True if the commit is present in one of the branches of the main repository
	"""
	# Revision may be a tag name. `branch_commits` doesn't work on tags
	if not _is_git_full_hash(revision):
	revision = self.get_tag_hash(tag_name=revision)
	repo = self._github_repository.html_url
	url = '/'.join([repo.rstrip('/'), 'branch_commits', revision])
	from scriptworker.task import get_decision_task_id
	cache_key = '{}-{}'.format(get_decision_task_id(context.task), url)
	async with _branch_commits_cache_lock:
	if cache_key in _branch_commits_cache:
	html_text = _branch_commits_cache[cache_key]
	else:
	html_data = await retry_request(context, url)
	html_text = html_data.strip()
	_branch_commits_cache[cache_key] = html_text
	# https://github.com/{repo_owner}/{repo_name}/branch_commits/{revision} just returns some \n
	# when the commit hasn't landed on the origin repo. Otherwise, some HTML data is returned - it
	# represents the branches on which the given revision is present.
	return html_text != ''

That call created issues like #331, where we ended up manually caching the responses.

Moving to the GraphQL API may help us in removing that caching logic

https://developer.github.com/v4/guides/migrating-from-rest/