Get user management page working, add permission checking in more places

inventory-server/auth/permissions.js

@@ -1,4 +1,19 @@
-const pool = global.pool;
+// Get pool from global or create a new one if not available
+let pool;
+if (typeof global.pool !== 'undefined') {
+  pool = global.pool;
+} else {
+  // If global pool is not available, create a new connection
+  const { Pool } = require('pg');
+  pool = new Pool({
+    host: process.env.DB_HOST,
+    user: process.env.DB_USER,
+    password: process.env.DB_PASSWORD,
+    database: process.env.DB_NAME,
+    port: process.env.DB_PORT,
+  });
+  console.log('Created new database pool in permissions.js');
+}
 
 /**
  * Check if a user has a specific permission