WIP auth, added Drift for database and refined shared_models for data exchange

backend/lib/authenticator.dart

@@ -0,0 +1,49 @@
+import 'dart:io';
+
+import 'package:backend/database.dart';
+import 'package:backend/service/db_access.dart';
+import 'package:dart_jsonwebtoken/dart_jsonwebtoken.dart';
+
+final jwtSecret = _getSecret();
+
+class Authenticator {
+  Future<String?> generateToken({required String username}) async {
+    final newUser = await Db.createUser(username: username);
+    if (newUser == null) return null;
+
+    final jwt = JWT(
+      {
+        'uid': newUser.uuid,
+      },
+    );
+
+    return jwt.sign(SecretKey(jwtSecret));
+  }
+
+  Future<User?> verifyToken(
+    String token,
+  ) async {
+    try {
+      final payload = JWT.verify(
+        token,
+        SecretKey(jwtSecret),
+      );
+
+      final payloadData = payload.payload as Map<String, dynamic>;
+
+      final uuid = payloadData['uuid'] as String;
+      return await Db.getUser(uuid);
+    } catch (e) {
+      return null;
+    }
+  }
+}
+
+String _getSecret() {
+  final secret = Platform.environment['JWT_TOKEN_SECRET'];
+  if (secret == null || secret.isEmpty) {
+    throw Exception('JWT secret not configured. Define JWT_TOKEN_SECRET in environment.');
+  } else {
+    return secret;
+  }
+}