admin page pulls in all groups at once, can cause long loading time

[blizzz]

By https://github.com/owncloud/core/blob/master/settings/admin.php#L55 all groups are loaded. On bigger LDAP setups (my test setup here > 7k groups) this will lead to long loading times.

To reproduce:

1. create a huge amount of groups (preferably with LDAP)
2. open admin page

cc @schiesbn

[PVince81]

This should probably be fixed by #8507 ?

[craigpg]

@blizz, can you confirm that this is fixed by #8507?

[blizzz]

@craigpg it is fixed in master, needs to be backported

[karlitschek]

@blizzz would be good if you could do that

[blizzz]

Just have seen, @butonic did already do a backport to 7 #10558 which was merged.
And also to 6 which is yet open #10576

[PVince81]

Note: groups will be pulled as well for the "exclude sharing from groups", so that part needs to be fixed as well.

[PVince81]

Another idea is to just use select2 with ajax like it was done here #10558
Might fix #10936 .

I'll give it a try as part of #10936

[butonic]

@blizzz @PVince81 I assume this can be closed?

[blizzz]

backport to stable6 is yet open #10576

[blizzz]

Issue fixed.