[RFE]Add API to view quota usage

[xrajesh]

Is your feature request related to a problem? Please describe.
When setting up token quota for users/ cluster, administrators need a way to view and update the tokens used.
This request is for adding APIs which can show the current token usage.

Describe the solution you'd like
REST APIs which take the user id as argument and give token usage information. We also need usage for the app level (cluster for OLS).

Describe alternatives you've considered
Viewing the usage in database , which is not a good user experience.
Additional context
Add any other context or screenshots about the feature request here.