LDAP plugin: force createUser to return new user's DN
LDAP plugin: force createUser to return new user's DN

LDAP plugins must change the createUser method to return the DN, as we
need this to update the cache.

Signed-off-by: Vinicius Cubas Brand <75c56e2cb0d529a7aba605116defc0edfc29a1c1@gmail.com>

andreas-p/nextcloud-server,andreas-p/nextcloud-server,nextcloud/server,nextcloud/server,andreas-p/nextcloud-server,nextcloud/server,andreas-p/nextcloud-server,andreas-p/nextcloud-server,nextcloud/server