I think you would want to do a GET request to the /people endpoint.
For example, we use emails as usernames, so if I hit the /firstname.lastname@example.org endpoint, the id field in the response contains my id (id: 1234).
Then I hit the /members/people/1234 endpoint to return my membership.
Hope that helps?
1 person found this helpful
There is a "magic" call :-) that covers this use case: GET /api/core/v3/people/@me returns the person object for the authenticated user.