A concise feature request title: **Support Server-Side Filtering for Empty Groups (`membersCount=0`) in Groups and Conversations APIs**

We would like to request support for filtering groups and conversations directly by membersCount=0 through the REST APIs. Currently, this requires fetching records and performing client-side filtering, which adds additional API calls and processing overhead. Having a server-side filter for empty groups would simplify implementation and improve efficiency for use cases involving inactive or abandoned groups.