Add reverse-proxy guard to support authentication proxy

app/Extensions/RemoteUserProvider.php

@@ -0,0 +1,67 @@
+<?php
+
+// Part of Firefly III (https://github.com/firefly-iii)
+// see https://github.com/firefly-iii/firefly-iii/blob/main/app/Support/Authentication/RemoteUserProvider.php
+
+namespace App\Extensions;
+
+use App\Models\User;
+use Illuminate\Contracts\Auth\Authenticatable;
+use Illuminate\Contracts\Auth\UserProvider;
+use Illuminate\Support\Str;
+use Exception;
+
+class RemoteUserProvider implements UserProvider
+{
+    /**
+     * @inheritDoc
+     */
+    public function retrieveById($identifier): User
+    {
+        $user = User::where('email', $identifier)->first();
+
+        // if (null === $user) {
+        //     $user = User::create(
+        //         [
+        //             'name' => $identifier,
+        //             'email' => $identifier,
+        //             'password' => bcrypt(Str::random(64)),
+        //         ]
+        //     );
+        // }
+
+        return $user;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function retrieveByToken($identifier, $token)
+    {
+        throw new Exception(sprintf('No implementation for %s', __METHOD__));
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function updateRememberToken(Authenticatable $user, $token)
+    {
+        throw new Exception(sprintf('No implementation for %s', __METHOD__));
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function retrieveByCredentials(array $credentials)
+    {
+        throw new Exception(sprintf('No implementation for %s', __METHOD__));
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function validateCredentials(Authenticatable $user, array $credentials)
+    {
+        throw new Exception(sprintf('No implementation for %s', __METHOD__));
+    }
+}