public static String coordinatorKey(String groupId, Uuid topicId, int partition) {
        Objects.requireNonNull(groupId);
        Objects.requireNonNull(topicId);

        return String.format("%s:%s:%d", groupId, topicId, partition);
    }
Calculates the coordinator key for finding a share coordinator.

@param groupId Group ID
@param topicId Topic ID
@param partition Partition index

@return The coordinator key
server-common/src/main/java/org/apache/kafka/server/group/share/ShareGroupHelper.java