Improvement: list-users for multiple relations at once

[Oscmage]

Today it is not possible to do something like this:

fga query list-users --relation owner,editor,viewer --object customer:customer_identifier_1 --user-filter user

You instead have to do 3 calls such as

fga query list-users --relation owner --object customer:customer_identifier_1 --user-filter user
fga query list-users --relation editor --object customer:customer_identifier_1 --user-filter user
fga query list-users --relation viewer --object customer:customer_identifier_1 --user-filter user

Our team have had this issue in two different scenario when we want to build something like an ADMIN page where you want to be able to determine which user has what relation to an object. The number of users are usually small for each object since it is a B2B scenario meaning it should be fine data wise.

See conversation from slack here: https://cloud-native.slack.com/archives/C06G1NNH47N/p1731660073851259