Feature: Add CRUID API endpoint to manage members' bookmarks

[constantine-nikolaou]

Members often bookmark interesting links on Slack or somewhere else. We hypothesise that they would like to keep track of them on MENAdevs Tilde platform.

Bookmark links have 3 privacy states:

1. Private (visible to the owner only)
2. Members-only (visible to the community)
3. Public: visible to every who has access to the member's profile