exercise.delete("/cant-do-exercises", verifyJwt, async (req, res) => {
  const {exerciseId, userId} = req.body;
  const currentUserId = req.userId;

  if (!exerciseId || !userId) {
    res.statusCode = 422;
    return res.json({
      data: null,
      error: {message: "Required query parameter [exerciseId|userId] is missing."}
    });
  }

  if (currentUserId !== userId) {
    try {
      if (!await trainerHasClient(currentUserId, userId)) {
        return res.json({
          data: null,
          error: {message: "No authorization to do this."}
        });
      }
    } catch (error) {
      return res.json({
        data: null,
        error: {message: error.message}
      });
    }
  }

  try {
    await knexDb("cant_do_exercises")
      .where("exerciseId", exerciseId)
      .andWhere("userId", userId)
      .delete();

    return res.json({
      data: {exerciseId},
      error: null
    });
  } catch (error) {
    return res.json({
      data: null,
      error: {message: error.message}
    });
  }
});