Support for LDAP/AD usernames and group names with special chars

Ranger usersync regards the forward slash ('/') as a separator character in the regex so it ignores it if you actually want to use it in your groupname. e.g. RRR/group_name_suffix

Using a different character like + in the regex works to get something like RRR+group_name_suffix but not RRR/group_name_suffix. / can be used as a domain separator in AD groups.