Fix backend user contract and add User-Employee-Customer linkage

- Add active field to User entity and users table
- Add userId linkage to Employee and Customer entities with unique constraints and FKs
- Add repository methods findByUserId and findAllByEmail
- Create UserBusinessLinkageService for shared employee/customer creation logic
- Create AuthenticationHelper utility for resolving authenticated users
- Update UserService to persist all user fields and create linked business entities
- Update AuthController register to set active and create linked customer
- Update DataInitializer to be idempotent and use shared linkage service
- Update Postman collection user endpoints with fullName, email, and active

src/main/resources/schema.sql

@@ -12,6 +12,7 @@ CREATE TABLE IF NOT EXISTS storeLocation (
 
 CREATE TABLE IF NOT EXISTS employee (
     employeeId BIGINT AUTO_INCREMENT PRIMARY KEY,
+    user_id BIGINT NULL,
     firstName VARCHAR(50) NOT NULL,
     lastName VARCHAR(50) NOT NULL,
     email VARCHAR(100) NOT NULL,
@@ -19,7 +20,8 @@ CREATE TABLE IF NOT EXISTS employee (
     role VARCHAR(50) NOT NULL,
     isActive BOOLEAN DEFAULT TRUE NOT NULL,
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
+    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+    CONSTRAINT uk_employee_user_id UNIQUE (user_id)
 );
 
 CREATE TABLE IF NOT EXISTS employeeStore (
@@ -32,12 +34,14 @@ CREATE TABLE IF NOT EXISTS employeeStore (
 
 CREATE TABLE IF NOT EXISTS customer (
     customerId BIGINT AUTO_INCREMENT PRIMARY KEY,
+    user_id BIGINT NULL,
     firstName VARCHAR(50) NOT NULL,
     lastName VARCHAR(50) NOT NULL,
     email VARCHAR(100) NOT NULL,
     phone VARCHAR(20) NOT NULL,
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
+    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+    CONSTRAINT uk_customer_user_id UNIQUE (user_id)
 );
 
 CREATE TABLE IF NOT EXISTS pet (
@@ -201,6 +205,7 @@ CREATE TABLE IF NOT EXISTS users (
     fullName VARCHAR(100),
     avatarUrl VARCHAR(255),
     role VARCHAR(20) NOT NULL,
+    active BOOLEAN NOT NULL DEFAULT TRUE,
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
     updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
 );
@@ -239,3 +244,7 @@ CREATE TABLE IF NOT EXISTS message (
     FOREIGN KEY (conversationId) REFERENCES conversation(id),
     FOREIGN KEY (senderId) REFERENCES users(id)
 );
+
+-- Add foreign keys for user_id linkage
+ALTER TABLE employee ADD CONSTRAINT fk_employee_user_id FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE SET NULL;
+ALTER TABLE customer ADD CONSTRAINT fk_customer_user_id FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE SET NULL;