Add Visible modes function from Organisation to Users too (#16069)

You can limit or hide organisations. This pull make it also posible for users

- new strings to translte
- add checkbox to user profile form
- add checkbox to admin user.edit form
- filter explore page user search
- filter api admin and public user searches
- allow admins view "hidden" users
- add app option DEFAULT_USER_VISIBILITY
- rewrite many files to use Visibility field
- check for teams intersection
- fix context output
- right fake 404 if not visible

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Andrew Thornton <art27@cantab.net>

modules/structs/user.go

@@ -43,6 +43,8 @@ type User struct {
 	Website string `json:"website"`
 	// the user's description
 	Description string `json:"description"`
+	// User visibility level option: public, limited, private
+	Visibility string `json:"visibility"`
 
 	// user counts
 	Followers    int `json:"followers_count"`