proxyPreparations should look-up projects by URL to avoid creating duplicates

[kriswest]

Describe the bug
I noticed that proxyPreparations is still looking up projects by project and name, where it should probably do so by URL instead:

git-proxy/src/proxy/index.ts

Lines 53 to 55 in df6406b

	defaultAuthorisedRepoList.forEach(async (x) => {
	const found = allowedList.find((y) => y.project === x.project && x.name === y.name);
	if (!found) {

This could result in creating a duplicate repo if the project or name wasn't set for a repo (as they are not required).

Expected behavior
Repositories with duplciate URLs aren't created accidentally