public TargetAssignmentBuilder<T> addOrUpdateMember(
        String memberId,
        T member
    ) {
        this.updatedMembers.put(memberId, member);
        return this;
    }
Adds or updates a member. This is useful when the updated member is
not yet materialized in memory.

@param memberId  The member id.
@param member    The member to add or update.
@return This object.
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/TargetAssignmentBuilder.java