[Multi-Tenant] Tenanted Admin UI Requests

[njlie]

The Admin UI should use the new identity management scheme for tenanted requests on the admin graphql api. The UI could present an input to collect the api secret that signatures should be signed with and add them to the browser session, if the UI does not detect that they have been set already.

• Input to collect tenant id & api secret for signature generation if unset
• Sign all requests from the UI to Admin API using api secret
• Augment all requests from UI to Admin API with tenantId header

Prerequisites:

• [Multi-Tenant] Use http-signatures to determine tenant identity during requests #2928