Quay should not allow to remove credentials during repository mirror sync up in progress

Description:

This is an issue found when mirror external repository, now after enabled mirror for a new image repository, provide required configurations, including external private repository, tags, schedule, credentials, click button "enable mirror", when sync up started, Quay allow operation to delete credentials, that's not reasonable, if users did operation "delete credentials", the sync up will be failed with unknown error.

Suggestions:

1. Users can only update mirror configurations when Scheduled mirroring is disabled
2. Users can only update mirror configurations when the status is not "sync up in progress"

Image: quay.io/projectquay/quay:0c65f88a

Steps:

1. Login Quay console
2. Create new image repository
3. Go to settings tab, set repository state as Mirror
4. Go to Mirror tag, provide required mirror configurations, including external private repository, tags, schedule, credentials, etc
5. Click button "enable mirror"
6. Wait for scheduled sync up to start
7. Check usage logs, when some tags are sync up, go to Mirror tag, delete credentials

Expected Results:

Quay should not allow users to delete credentials.

Actual Results:

Quay allow user to delete credentials even the current status is "Sync up in progress"