Support Read-Only Group Access for Restricted or Banned Users

Introduce a configurable group moderation mode that allows administrators to restrict a user’s participation without completely removing their access to the group conversation. Currently, banning or kicking a user immediately revokes access to the group and its message history. The requested enhancement is to support a read-only state where restricted users can continue viewing the group’s existing messages but cannot send new messages or receive messages sent after the restriction is applied. This would enable applications to implement user-blocking workflows that comply with App Store and Google Play policies while preserving conversation history. Additionally, for scenarios such as two-member groups, the solution should support preventing the remaining participant from sending new messages as well, effectively freezing the conversation while maintaining historical access. This feature would provide greater flexibility for moderation and safety use cases without requiring custom implementations.