Refactor database DiscoveryResourceChecker

[greedy52]

Moving discoveryResourceChecker from lib/srv/db/watcher.go to lib/srv/db/cloud/resource_checker.go

This changes prepares for adding database URL validation as more checkers will be implemented

[greedy52]

moved from watcher.go without logic change

[greedy52]

moved from watcher.go but now returns error

[GavinFrazar]

LGTM

as for the data race detected during the test, I believe this is caused by the resource watcher's collector returning all of its collected resources every time a database is created:

teleport/lib/services/watcher.go

Lines 864 to 873 in 3ecc0f0

	case types.OpPut:
	database, ok := event.Resource.(types.Database)
	if !ok {
	p.Log.Warnf("Unexpected resource type %T.", event.Resource)
	return
	}
	p.current[database.GetName()] = database
	select {
	case <-ctx.Done():
	case p.DatabasesC <- resourcesToSlice(p.current):

Not sure why the extra test case you added caused the race detector to trip now - I can't reproduce a data race failure if I remove the extra test case. I don't think it's caused by these changes though

[greedy52]

Not sure why the extra test case you added caused the race detector to trip now - I can't reproduce a data race failure if I remove the extra test case. I don't think it's caused by these changes though

I believe the race happens because the last test case (launching heartbeat/iam service etc.) and the new test case (applyResourceMatchersToDatabases) race on db5 that's stored in the test auth server. Let me work on a fix.

[greedy52]

@GavinFrazar @smallinsky

I've added a fix for the race d77047f.

The idea is to ensure that we don't change the attributes of databases in s.monitoredDatabases. And we use database.Copy() for proxiedDatabases. Attributes of databases in proxiedDatabases can be changed but only to "status" not "spec".

Let me know what you think. Thanks!

[GavinFrazar]

we should backport the race fix to v13 as well

[public-teleport-github-review-bot]

@greedy52 See the table below for backport results.

Branch	Result
branch/v13	Failed