Support updating custom claims in updateUser()

[brettwillis]

Closes #1876

Summary

Currently, the custome user claims can be updated with setCustomUserClaims(), and the user details can be updated with updateUser(). Both use same /accounts:update REST API under the hood.

This allows account and claims info to be updated in one hit using the updateUser() method.

[brettwillis]

@lahirumaramba any thoughts on this?

[brettwillis]

@lahirumaramba @prameshj I completed the test suite adding integration tests and unit tests. All relevant tests that were applied to setCustomUserClaims() are applied to the relevant claims functionality in updateUser(). Would appreciate a moment to review 🙏🏼 .