Refactor generate method in MysqlDatabaseConfig class

The generate method in the MysqlDatabaseConfig class had an error that caused an undefined local variable or method 'config'. The error was due to using the config variable before it was initialized. The solution was to move the code that sets b2_enabled and adds b2 to config after the config variable is initialized. This commit fixes the error by modifying the generate method in the MysqlDatabaseConfig class.

mysql_database_config.rb

@@ -19,17 +19,7 @@ class MysqlDatabaseConfig
 
       backup_dir = prompt('Backup Directory', default: '.')
 
-      b2_enabled = prompt_bool('Enable Backblaze B2?', default: false)
+      @config = {
-      config['b2_enabled'] = b2_enabled
-      if b2_enabled
-        config['b2'] = {
-          'key_id' => @b2_key_id,
-          'application_key' => @b2_application_key,
-          'bucket_name' => @b2_bucket_name
-        }
-      end
-
-      config = {
         'mysql' => {
           'host' => mysql_host,
           'username' => mysql_username,
@@ -38,15 +28,20 @@ class MysqlDatabaseConfig
         'backup_dir' => backup_dir
       }
 
+      b2_enabled = prompt_bool('Enable Backblaze B2?', default: false)
+      @config['b2_enabled'] = b2_enabled
       if b2_enabled
-        config['b2'] = {
+        @b2_key_id = prompt('B2 Key ID')
+        @b2_application_key = prompt('B2 Application Key')
+        @b2_bucket_name = prompt('B2 Bucket Name')
+        @config['b2'] = {
           'key_id' => @b2_key_id,
           'application_key' => @b2_application_key,
           'bucket_name' => @b2_bucket_name
         }
       end
 
-      File.write(@config_file, JSON.pretty_generate(config))
+      File.write(@config_file, JSON.pretty_generate(@config))
       puts "Config file generated: #{@config_file}"
     end
   end