This is a port of gogs/gogs#4398

The only changes made by myself are:

Add locales
Add some JS to the UI
Otherwise all code credit goes to @aboron

Resolves #10829

Signed-off-by: jolheiser <john.olheiser@gmail.com>
Co-authored-by: zeripath <art27@cantab.net>

* Add restricted user filter to LDAP authentification

* Fix unit test cases

* Add LDAP Key Synchronization feature

Signed-off-by: Magnus Lindvall <magnus@dnmgns.com>

* Add migration: add login source id column for public_key table

* Only update keys if needed

* Add function to only list pubkey synchronized from ldap

* Only list pub ssh keys synchronized from ldap. Do not sort strings as ExistsInSlice does it.

* Only get keys belonging to current login source id

* Set default login source id to 0

* Some minor cleanup. Add integration tests (updete dep testify)