docs: public long[] matchIndices() {
          // Leader index is appended at the end of array in AppendSuccessResponseHandlerTask
          // That's why we add one more empty slot.
          long[] indices = new long[followerStates.size() + 1];
          int ix = 0;
          for (FollowerState state : followerStates.values()) {
              indices[ix++] = state.matchIndex();
          }
          return indices;
      }