Ensure that requests are not forwarded for unknown repositories

[kriswest]

Describe the bug
In #1043 it was observed that requests are forwarded to github.com for unknown repositories in some cases:

E.g.

processing request URL: '/gitlab.com/gitlab-community/meta.git/info/refs?service=git-upload-pack'
proxy keys registered:  ["/github.com/"]
        using fallback
Action processed: Allowed
    Request URL: /gitlab.com/gitlab-community/meta.git/info/refs?service=git-upload-pack
    Host:        127.0.0.1:61485
    User-Agent:  git/2.42.0
Request resolved to https://github.com/gitlab.com/gitlab-community/meta.git/info/refs?service=git-upload-pack

This is in the proxy route tests at:

git-proxy/test/testProxyRoute.test.js

Line 427 in 9679618

it('should be restarted by the api and stop proxying requests for a host (e.g. gitlab.com) when the last project at that host is DELETED via the API', async function () {

The test currently passes as the resulting URL is not a project at github.com and hence a 404 is returned through the proxy. However, pull requests - likely any requests - should not be forwarded unless the repository is known/configured in git proxy. This appears to be the intent for pull requests as CheckRepoInAuthorisedList is the only default processor in the pull chain:

git-proxy/src/proxy/chain.ts

Lines 26 to 28 in 9679618

	const pullActionChain: ((req: any, action: Action) => Promise<Action>)[] = [
	proc.push.checkRepoInAuthorisedList,
	];

. However, on instrumenting the code it appears NOT to be getting run. Why that is needs to be debugged and new test implemented confirming that you can't fetch or pull a repo from github that is NOT in authorized list.

To Reproduce
Run the tests and check the output for test 'should be restarted by the api and stop proxying requests for a host (e.g. gitlab.com) when the last project at that host is DELETED via the API'. "Action processed: Blocked" should appear in the log for that test.

Alternatively, manually construct a URL that git-proxy would produce for a gihub repo, but hasn't as its not configured. Then add that as a remote and attempt to fetch/pull from it.

Expected behavior
"Action processed: Blocked" should always appear in the log for operations on unknown repositories.

Additional context
There exists a test that confirms we run NO actions for anything other than a pull or push request. Whereas I think we should always check that the repository is known before forwarding any request. Otherwise, we risk the proxy being abused in unexpected ways.