This adds support for the ADLDAP_AUTH_FILTER env var, and the

ldap_auth.custom_filter config option. These are optional.

If provided, the custom filter will be applied to the LDAP query
using the FireflyIII\Scopes\LdapFilterScope class.

This allows the integrator to specify a custom LDAP filter.

app/Scopes/LdapFilterScope.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace FireflyIII\Scopes;
+
+use Adldap\Query\Builder;
+use Adldap\Laravel\Scopes\ScopeInterface;
+
+class LdapFilterScope implements ScopeInterface {
+    /**
+     * If the ADLDAP_AUTH_FILTER is provided, apply the filter to the LDAP query.
+     * @param Builder $query
+     * @return void
+     */
+    public function apply(Builder $query)
+    {
+        $filter = config('ldap_auth.custom_filter');
+        if ( $filter ) {
+            $query->rawFilter($filter);
+        }
+    }
+}