getNotMemberCommunities = async (req, res) => {
  try {
    const communities = await Community.find({
      members: {
        $nin: [req.userId],
      },
      bannedUsers: {
        $nin: [req.userId],
      },
    })
      .select("_id name banner description members")
      .lean();

    res.status(200).json(communities);
  } catch (error) {
    res.status(500).json({
      message: "Error getting communities",
    });
  }
}
Retrieves up to 10 public communities that the current user is not a member of
and has not been banned from, including their name, banner image, description,
and member count, sorted by the number of members.

@route GET /communities/not-member