Implement a flexible search in LDAP for the REST API auth

[belyaev-andrey]

Implement a flexible search in LDAP for the REST API controller LdapAuthController. Now we have a hardcoded simple method

    protected String buildPersonFilter(String login) {
        AndFilter filter = new AndFilter();
        filter.and(new EqualsFilter("objectclass", "person"))
                .and(new EqualsFilter(ldapUserLoginField, login));
        return filter.encode();
    }

Which cannot be overridden properly because overriding a Controller with mapping in Spring might be a challenging task.

Suggestion:

Extract this method to a service that will build the filter. Services can be overridden easily in CUBA, therefore, users will be able to create their own filters for LDAP search.