Add a user to multiple groups in a single API call

Today, adding a member is always scoped to one group at a time. The Add Members endpoint can add many users to a single group, but there is no way to do the reverse — add one user to several groups at once. Customers have to loop and make a separate call per group, and handle partial failures themselves.

Requested by Rakesh Tiwari (truleague) via the Docs assistant.

Ask: a way to pass a user and a list of groups (with scope) in one request, returning per-group success/failure so partial results are visible.

Use cases: signup with team or interest selection, roster and org onboarding, admin bulk actions.