Add social features [1st part]

[SamR1]

related to: https://github.com/SamR1/FitTrackee/issues/125, https://github.com/SamR1/FitTrackee/issues/296, https://github.com/SamR1/FitTrackee/issues/298, https://github.com/SamR1/FitTrackee/issues/299, https://github.com/SamR1/FitTrackee/issues/381, https://github.com/SamR1/FitTrackee/issues/382

🚧 WIP, some features may change 🚧

• [x] add visibility levels to workouts (=privacy levels)

  • [x] 3 levels: private, followers_only, public
  • [x] distinct visibility levels between workout data (title, date, distance...) and geolocation-related data (map, analysis) (note: workout notes are only visible to the workout owner)
  • [x] by default, all data are private (default visiblities can be changed in user preferences)

• [x] timeline on dashboard displaying the workouts a user can see

• [x] a user can (un-)follow another user

  • [x] by default, a follow request must be manually approved (default value can be changed in user preferences)
  • [x] users directory
    • [x] preference to hide user account. By default, user is hidden.

• [x] a user can comment a workout

  • [x] 3 levels: private (only mentioned users can view comments), followers_only, public
  • [x] a user can edit or delete his comment
  • [x] mention suggestions autocomplete

• [x] a user can (un-)like a workout or a comment

• [ ] notifications on UI

  • [x] on follow request, new comment on a workout, new reply on a comment, like on a workout or a comment
  • [x] mark all notifications as read
  • [ ] new user for admins
  • user warning (see https://github.com/SamR1/FitTrackee/issues/382)
  • workout suspension (see https://github.com/SamR1/FitTrackee/issues/382)
  • comment suspension (see https://github.com/SamR1/FitTrackee/issues/382)

• [x] improve users preferences display

• [x] markdown support in Comments and Notes

• [x] a user can (un-)block another user

  • [x] display blocked users list in user profile

• [ ] [in progress 🔄]: moderation tools (see https://github.com/SamR1/FitTrackee/issues/382)

• [ ] TODO: check equipments feature

  • Notes: equipment is only visible to its owner

• [ ] TODO: check new description field (same visibility as workout) and updates on notes field

• [ ] TODO: update dark mode

• [ ] TODO: update user export

• [ ] TODO: default privacy policy update

• [ ] TODO: update documentation