Create Auth Session for Existing User Invite

NOTE: In order for the session cookie to be set properly this API needs to be redirected to from the browser. The redirect URL should use the vanity domain of the tenant that the session is associated to.

Creates a new auth session for the user and returns a response containing a redirect to the configured redirect location. The response will also include the session cookie.

The redirect URL that gets returned will resolve in the following order:

• If an Existing User Invite Workflow custom redirect URL is configured, that will be returned.
• Otherwise, the application login URL is returned.