Added core data models, repositories, and utilities

lifetimer/lib/data/models/activity_model.dart

@@ -0,0 +1,56 @@
+import 'package:equatable/equatable.dart';
+
+class Activity extends Equatable {
+  final String id;
+  final String userId;
+  final String type;
+  final Map<String, dynamic>? payload;
+  final DateTime createdAt;
+
+  const Activity({
+    required this.id,
+    required this.userId,
+    required this.type,
+    this.payload,
+    required this.createdAt,
+  });
+
+  Activity copyWith({
+    String? id,
+    String? userId,
+    String? type,
+    Map<String, dynamic>? payload,
+    DateTime? createdAt,
+  }) {
+    return Activity(
+      id: id ?? this.id,
+      userId: userId ?? this.userId,
+      type: type ?? this.type,
+      payload: payload ?? this.payload,
+      createdAt: createdAt ?? this.createdAt,
+    );
+  }
+
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'user_id': userId,
+      'type': type,
+      'payload': payload,
+      'created_at': createdAt.toIso8601String(),
+    };
+  }
+
+  factory Activity.fromJson(Map<String, dynamic> json) {
+    return Activity(
+      id: json['id'] as String,
+      userId: json['user_id'] as String,
+      type: json['type'] as String,
+      payload: json['payload'] as Map<String, dynamic>?,
+      createdAt: DateTime.parse(json['created_at'] as String),
+    );
+  }
+
+  @override
+  List<Object?> get props => [id, userId, type, payload, createdAt];
+}