Allow filter on target of a navigation collection for users and groups
Enable filtering and casting on the target for a navigation collection. For example "get the users that are members of a group, even though the group contains users, groups and service principals. Additionally allow me to do things like find all the members of this group that are in "sales" department.
This capability is now available in Microsoft Graph public preview. For an example please see https://docs.microsoft.com/en-us/graph/api/group-list-members?view=graph-rest-beta&tabs=http#example-5-use-filter-to-get-group-membership-with-a-display-name-that-starts-with-the-letter-a-including-a-count-of-returned-objects.
NOTE: you’ll need to use a custom HTTP request header and request $count too, to enable this query capability.
See also related queries in the changelog entry https://docs.microsoft.com/en-us/graph/changelog#identity-and-access-azure-ad
Add support for isof per the odata spec rather than inventing your own implementation.