Add support for LDAP-based authentication

[paulmillar]

I believe that ALISE currently only supports OIDC-based authentication. For facility-local authentication, this requires the facility deploying ALISE has a working OP, such as KeyCloak,

Although many facilities have an OP, there are also many facilities who have not done so.

Instead, these facilities often support RPs accepting username+password credentials directly. The username+password is verified by the RP contacting an LDAP service and authentication ("binding") to that LDAP service using a username+password credential. If the connection is established then the password is correct. The subsequent LDAP connection may be used to query additional information about the user (if needed by ALISE).

Therefore, it would be helpful if ALISE was updated to support LDAP-based authentication.