[BUG] Group membership search default sort order is inconsistent

[spwitt]

Group membership search default sort order is inconsistent

Description

The default sort order for the /api/group/member/search API is not consistent. The results are sorted by insertInstant, which is not unique. It is possible to get different results with duplicate API calls.

Observed versions

1.51.1

Steps to reproduce

1. Create a Group
2. Add 1000+ members to the group
3. Call the group membership search API many times
4. Look for different group membership results from identical API calls

Expected behavior

The group membership search API should return results in the same order each time it is called with the default sort options.