[2.x] Case insensitive DN comparison

[bonroyage]

Ported from #607

---

I noticed while I was making an authentication rule, that the validation would fail, even though I was sure that the DN was correctly given.

Turns out that providing a string wouldn't work while providing the same string within Group::findOrFail would work if the DN provided by the LDAP server has a different case, like cn=foo,dc=local,dc=com.

Works:

return $this->user->groups()->exists(
    Group::findOrFail('CN=foo,DC=local,DC=com')
);

Doesn't work:

return $this->user->groups()->exists(
    'CN=foo,DC=local,DC=com'
);

[stevebauman]

Thanks again @bonroyage! I’ll create a new release shortly.