Add backend API for personal finance management application

- Introduced a comprehensive backend API using TypeScript, Fastify, and PostgreSQL.
- Added essential files including architecture documentation, environment configuration, and Docker setup.
- Implemented RESTful routes for managing assets, liabilities, clients, invoices, and cashflow.
- Established a robust database schema with Prisma for data management.
- Integrated middleware for authentication and error handling.
- Created service and repository layers to adhere to SOLID principles and clean architecture.
- Included example environment variables for development, staging, and production setups.

backend-api/src/controllers/DebtPaymentController.ts

@@ -0,0 +1,94 @@
+import {FastifyRequest, FastifyReply} from 'fastify';
+import {DebtPaymentService} from '../services/DebtPaymentService';
+import {getUserId} from '../middleware/auth';
+import {z} from 'zod';
+
+const createPaymentSchema = z.object({
+  accountId: z.string().uuid(),
+  amount: z.number().min(0.01),
+  paymentDate: z.string().transform(str => new Date(str)),
+  notes: z.string().optional(),
+});
+
+/**
+ * Controller for DebtPayment endpoints
+ * Implements Single Responsibility Principle - handles only HTTP layer
+ */
+export class DebtPaymentController {
+  constructor(private paymentService: DebtPaymentService) {}
+
+  /**
+   * Create a new debt payment
+   */
+  async create(request: FastifyRequest, reply: FastifyReply) {
+    const userId = getUserId(request);
+    const data = createPaymentSchema.parse(request.body);
+
+    const payment = await this.paymentService.create(userId, data);
+
+    return reply.status(201).send({payment});
+  }
+
+  /**
+   * Get all debt payments
+   */
+  async getAll(request: FastifyRequest, reply: FastifyReply) {
+    const userId = getUserId(request);
+    const {accountId, startDate, endDate} = request.query as {
+      accountId?: string;
+      startDate?: string;
+      endDate?: string;
+    };
+
+    if (accountId) {
+      const payments = await this.paymentService.getByAccount(accountId, userId);
+      return reply.send({payments});
+    }
+
+    if (startDate && endDate) {
+      const payments = await this.paymentService.getByDateRange(
+        userId,
+        new Date(startDate),
+        new Date(endDate)
+      );
+      return reply.send({payments});
+    }
+
+    const payments = await this.paymentService.getAllByUser(userId);
+    return reply.send({payments});
+  }
+
+  /**
+   * Get a single debt payment
+   */
+  async getOne(request: FastifyRequest, reply: FastifyReply) {
+    const userId = getUserId(request);
+    const {id} = request.params as {id: string};
+
+    const payment = await this.paymentService.getById(id, userId);
+
+    return reply.send({payment});
+  }
+
+  /**
+   * Delete a debt payment
+   */
+  async delete(request: FastifyRequest, reply: FastifyReply) {
+    const userId = getUserId(request);
+    const {id} = request.params as {id: string};
+
+    await this.paymentService.delete(id, userId);
+
+    return reply.status(204).send();
+  }
+
+  /**
+   * Get total payments
+   */
+  async getTotalPayments(request: FastifyRequest, reply: FastifyReply) {
+    const userId = getUserId(request);
+    const totalPayments = await this.paymentService.getTotalPayments(userId);
+
+    return reply.send({totalPayments});
+  }
+}