ldap auth support

[cyberb]

Simple ldap auth support:

--ldap-uri=ldap://localhost:389
--ldap-bind-dn="cn={username},ou=users,dc=example,dc=com"

Where {username} will be replaced with username from the auth web form.

Also support for outdir override as when using in a read-only binary more relative dir is not writable

--outdir-samples=/path/to/dir

This was created and tested for Syncloud self-hosted platform (https://github.com/syncloud/platform) - https://github.com/syncloud/stable-diffusion