Summary:
Currently TP allows to enable authentication via API token.
Once that is enabled - YBA will not be able to register customer/universe.
This adds this API token to TP metadata in YBA and uses it for authentication in case it's defined.

Test Plan:
Start TP without API token defined.
Register customer and universe through YBA UI.
Make sure TP UI works in YBA.
Unregister universe and customer through UBA UI.
Restart TP with API token defined.
Register customer and universe through YBA UI.
Make sure TP UI is not working (as we have not auth for this part yet)
Unregister universe and customer through UBA UI.
Try to register customer with wrong and empty password. Make sure error is shown.

Reviewers: rmadhavan, #yba-api-review!

Reviewed By: rmadhavan

Subscribers: sanketh, yugaware

Differential Revision: https://phorge.dev.yugabyte.com/D38673