[ECM-30] Basic implementation of Payment Service

[arturgesiarz]

Implemented a complete Payment Service prototype

Core Functionality

• Payment Creation & Management - Generate unique payment links for orders
• Payment Processing - Simulate payment completion with status tracking
• Automatic Expiration - Quartz Scheduler automatically expires payments after 10 minutes
• Status Management - Track payment lifecycle (PENDING → PAID/EXPIRED/CANCELLED/FAILED)

Entities

• Payment - Main payment entity with comprehensive status tracking
• PaymentEvent - Event store for Outbox Pattern implementation

Database Schema:

Links

• Linear Issue: ECM-30
• Database Schema: Vertabelo