Get the calling service account

Returns the identity of the service account that owns the access token used for this request. Use it to confirm that a token works and to see which scopes and nodes it can reach. Any valid access token is accepted, whatever scopes it grants. Node access is re-read on every request, so a change to the nodes takes effect on the next call. Scopes are fixed when the token is issued: request a new token to pick up a newly granted scope. Removing a scope, revoking the account or rotating its credentials invalidates existing tokens immediately. scopes lists what this token grants, which can be fewer than the account holds. business_node_ids lists the nodes the account can read. An empty list means the account can read nothing. The response is never cached.