Add user promotion endpoint

🔧 Admin Management:
- Add api/admin/promote-user.js endpoint
- Allows promoting users to admin role by username or userId
- Checks for existing admin status
- Returns updated user info with roles
- Handles database errors gracefully

Usage: POST /api/admin/promote-user with { username: 'testuser' }

api/admin/promote-user.js

@@ -0,0 +1,128 @@
+const { Pool } = require('pg');
+
+const pool = new Pool({
+  connectionString: process.env.DATABASE_URL,
+  ssl: process.env.NODE_ENV === 'production' ? { rejectUnauthorized: false } : false,
+});
+
+export default async function handler(req, res) {
+  if (req.method !== 'POST') {
+    return res.status(405).json({ error: 'Method not allowed' });
+  }
+
+  try {
+    const body = JSON.parse(req.body || '{}');
+    const { username, userId } = body;
+
+    if (!username && !userId) {
+      return res.status(400).json({ 
+        error: 'Either username or userId is required' 
+      });
+    }
+
+    const client = await pool.connect();
+
+    try {
+      // Find the user
+      let userQuery;
+      let userParams;
+      
+      if (userId) {
+        userQuery = 'SELECT id, username, email FROM users WHERE id = $1';
+        userParams = [userId];
+      } else {
+        userQuery = 'SELECT id, username, email FROM users WHERE username = $1';
+        userParams = [username];
+      }
+
+      const userResult = await client.query(userQuery, userParams);
+      
+      if (userResult.rows.length === 0) {
+        return res.status(404).json({ 
+          error: 'User not found' 
+        });
+      }
+
+      const user = userResult.rows[0];
+
+      // Check if user is already an admin
+      const adminCheckQuery = `
+        SELECT ur.user_id 
+        FROM user_roles ur 
+        JOIN roles r ON ur.role_id = r.id 
+        WHERE ur.user_id = $1 AND r.name = 'admin'
+      `;
+      
+      const adminCheck = await client.query(adminCheckQuery, [user.id]);
+      
+      if (adminCheck.rows.length > 0) {
+        return res.status(200).json({
+          success: true,
+          message: 'User is already an admin',
+          user: {
+            id: user.id,
+            username: user.username,
+            email: user.email
+          }
+        });
+      }
+
+      // Get admin role ID
+      const roleResult = await client.query(
+        'SELECT id FROM roles WHERE name = $1',
+        ['admin']
+      );
+
+      if (roleResult.rows.length === 0) {
+        return res.status(500).json({ 
+          error: 'Admin role not found in database' 
+        });
+      }
+
+      const adminRoleId = roleResult.rows[0].id;
+
+      // Add user to admin role
+      await client.query(
+        'INSERT INTO user_roles (user_id, role_id) VALUES ($1, $2)',
+        [user.id, adminRoleId]
+      );
+
+      // Get updated user info with roles
+      const updatedUserQuery = `
+        SELECT 
+          u.id, u.username, u.email, u.first_name, u.last_name,
+          ARRAY_AGG(DISTINCT r.name) as roles
+        FROM users u
+        LEFT JOIN user_roles ur ON u.id = ur.user_id
+        LEFT JOIN roles r ON ur.role_id = r.id
+        WHERE u.id = $1
+        GROUP BY u.id, u.username, u.email, u.first_name, u.last_name
+      `;
+
+      const updatedUser = await client.query(updatedUserQuery, [user.id]);
+
+      res.status(200).json({
+        success: true,
+        message: 'User successfully promoted to admin',
+        user: {
+          id: updatedUser.rows[0].id,
+          username: updatedUser.rows[0].username,
+          email: updatedUser.rows[0].email,
+          firstName: updatedUser.rows[0].first_name,
+          lastName: updatedUser.rows[0].last_name,
+          roles: updatedUser.rows[0].roles || []
+        }
+      });
+
+    } finally {
+      client.release();
+    }
+
+  } catch (error) {
+    console.error('Promote user error:', error);
+    res.status(500).json({ 
+      error: 'Internal server error',
+      details: error.message 
+    });
+  }
+}