public boolean isStaticMemberFenced(
        String groupInstanceId,
        String memberId
    ) {
        String existingMemberId = staticMemberId(groupInstanceId);
        return existingMemberId != null && !existingMemberId.equals(memberId);
    }
Verify the member id is up to date for static members. Return true if both conditions met:
  1. given member is a known static member to group
  2. group stored member id doesn't match with given member id

@param groupInstanceId  the group instance id.
@param memberId         the member id.
@return whether the static member is fenced based on the condition above.
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/classic/ClassicGroup.java