User's k8s namespace creation routine

[skabashnyuk]

Is your task related to a problem? Please describe.

Quite a few issues #19236 #19972
related to the way how and when a user's namespace should/can be created. I would like to propose a way how
we can solve several issues.

• Pre-create the User's namespace if it does not exist. That should happen regularly since it can be deleted and we can't resist that.
• For devworkspace engine, we need to prepopulate k8s namespace with self-signed secretes, proxy settings etc.
• We would like to make the user's profile/preferences more k8s friendly (migrate from PostgreSQL)

Describe the solution you'd like

• To have the REST Service on the Che server-side that will initiate k8s namespace provisioning and create CheUser CR in the user’s namespace. This method can be called from:
  On dashboard page load, from dashboard before each workspace related operation, before factory resolve
  From traefik on each request, with some caching (1-5 minutes)
• To have a controller that will manage the creation of necessary configmaps in user's namespace
• CheUser CR can later be used to store user’s preferences.

Implementation

• REST Service on the Che server-side that will initiate k8s namespace provisioning #20165
• [Dashboard] Ensure k8s namespace exists before workspace related operation #20167
• [devworkspace-che-operator] Prototype and plan of controller that is reconciling resources in user's namespace #20219
• [STEP3] user's namespace provisioning  #20168
• Create CheUser CR when pre-creating k8s namespace #20169
• An admin should be able to specify Secrets, ConfigMaps and PersistentVolumesClaims that need to be provisioned on each user's namespace #20501
• Support custom certificates for git hosts for devworkspaces #20528

Describe alternatives you've considered

n/a

Additional context

• Factory acceptance fails if there is no k8s namespace yet #19236
• Implement an ability to preCreate namespaces for users with privileged SA #19972