Simple ldap auth

[cyberb]

This is a simple ldap authentication with admin detection.
Here is the example config:

export PHOTOPRISM_LDAP_ENABLED="true"
export PHOTOPRISM_LDAP_URI="ldap://localhost:389"
export PHOTOPRISM_LDAP_BIND_DN="cn={username},ou=users,dc=syncloud,dc=org"
export PHOTOPRISM_LDAP_ADMIN_GROUP_DN="cn=syncloud,ou=groups,dc=syncloud,dc=org"
export PHOTOPRISM_LDAP_ADMIN_GROUP_FILTER="(memberUid={username})"
export PHOTOPRISM_LDAP_ADMIN_GROUP_ATTRIBUTE="memberUid"

[CLAassistant]

All committers have signed the CLA.

[johnmmcgee]

This is awesome!