Fix MySQL foreign key constraint errors by ensuring unsigned integer consistency

- Update user table migration to create unsigned id column for MySQL
- Add unsigned attribute to token.user_id foreign key
- Add foreign key before create() in GDPR Phase 3 migration
- Make created_by nullable in GDPR Phase 4 data retention policies

Fixes errno: 150 'Foreign key constraint is incorrectly formed' errors
when migrating on empty MySQL database. All id columns are now unsigned
on MySQL for consistency with newer Phinx defaults.

Author: Vitexus

db/migrations/20160203130652_user.php

@@ -19,6 +19,10 @@ class User extends AbstractMigration
 {
     public function change(): void
     {
+        // Check if the database is MySQL to handle unsigned integers
+        $databaseType = $this->getAdapter()->getOption('adapter');
+        $unsigned = ($databaseType === 'mysql') ? ['signed' => false] : [];
+
         // Migration for table users
         $table = $this->table('user');
         $table
@@ -37,7 +41,7 @@ public function change(): void
 
         if ($this->adapter->getAdapterType() !== 'sqlite') {
             $table
-                ->changeColumn('id', 'integer', ['identity' => true])
+                ->changeColumn('id', 'integer', array_merge(['identity' => true], $unsigned))
                 ->save();
         }
     }

db/migrations/20221012185432_token.php

@@ -30,12 +30,16 @@ final class Token extends AbstractMigration
      */
     public function change(): void
     {
+        // Check if the database is MySQL to handle unsigned integers
+        $databaseType = $this->getAdapter()->getOption('adapter');
+        $unsigned = ($databaseType === 'mysql') ? ['signed' => false] : [];
+
         $table = $this->table('token');
         $table
             ->addColumn('token', 'string', ['limit' => 64])
             ->addColumn('start', 'datetime', ['default' => 'CURRENT_TIMESTAMP'])
             ->addColumn('until', 'datetime', ['null' => true])
-            ->addColumn('user_id', 'integer', ['null' => false])
+            ->addColumn('user_id', 'integer', array_merge(['null' => false], $unsigned))
             ->addForeignKey('user_id', 'user', 'id', ['constraint' => 'user_must_exist'])
             ->create();
     }

db/migrations/20241020190000_gdpr_phase3_security_enhancements.php

@@ -133,16 +133,17 @@ private function createTwoFactorAuthTables(): void
             ->addColumn('created_at', 'timestamp', ['default' => 'CURRENT_TIMESTAMP'])
             ->addColumn('last_used', 'timestamp', ['null' => true])
             ->addColumn('recovery_codes_used', 'json', ['null' => true])
-            ->addIndex(['user_id'], ['unique' => true])
-            ->create();
+            ->addIndex(['user_id'], ['unique' => true]);
 
-        // Add foreign key constraint if not SQLite
+        // Add foreign key constraint before create() if not SQLite
         if ($this->adapter->getAdapterType() !== 'sqlite') {
             $table->addForeignKey('user_id', 'user', 'id', [
                 'delete' => 'CASCADE',
                 'update' => 'NO_ACTION',
-            ])->save();
+            ]);
         }
+
+        $table->create();
     }
 
     /**

db/migrations/20250120185000_gdpr_phase4_data_retention.php

@@ -119,7 +119,7 @@ private function createDataRetentionPoliciesTable(): void
         $table->addColumn('legal_basis', 'string', ['limit' => 255, 'null' => true, 'comment' => 'Legal basis for retention period'])
             ->addColumn('description', 'text', ['null' => true, 'comment' => 'Human-readable description of the policy'])
             ->addColumn('enabled', 'boolean', ['default' => true, 'null' => false, 'comment' => 'Whether this policy is active'])
-            ->addColumn('created_by', 'integer', array_merge(['null' => false], $unsigned))
+            ->addColumn('created_by', 'integer', array_merge(['null' => true], $unsigned))
             ->addColumn('created_at', 'timestamp', ['default' => 'CURRENT_TIMESTAMP'])
             ->addColumn('updated_at', 'timestamp', ['default' => 'CURRENT_TIMESTAMP', 'update' => 'CURRENT_TIMESTAMP'])
             ->addIndex(['policy_name'], ['unique' => true])
@@ -131,7 +131,7 @@ private function createDataRetentionPoliciesTable(): void
         // Add foreign key constraint if not SQLite
         if ($this->adapter->getAdapterType() !== 'sqlite') {
             $table->addForeignKey('created_by', 'user', 'id', [
-                'delete' => 'RESTRICT',
+                'delete' => 'SET_NULL',
                 'update' => 'NO_ACTION',
             ])->save();
         }
@@ -412,8 +412,9 @@ private function enhanceExistingTablesWithRetentionFields(): void
     private function insertDefaultRetentionPolicies(): void
     {
         // Get first admin user ID for created_by field
+        // If no users exist yet, use NULL (created_by column allows null)
         $adminUser = $this->fetchRow('SELECT id FROM user WHERE enabled = 1 ORDER BY id LIMIT 1');
-        $adminUserId = $adminUser['id'] ?? 1;
+        $adminUserId = $adminUser['id'] ?? null;
 
         $policies = [
             [