setMessageSource method

Sets the MessageSource used for resolving internationalized messages.

The message source provides internationalization (i18n) capabilities for applications that need to support multiple languages and locales.

Message Source Features:

• Parameterized Messages: Support for placeholders and arguments
• Locale Resolution: Automatic locale detection and fallback
• Hierarchical Sources: Parent-child message source relationships
• Reloadable Bundles: Hot-reload of message bundles in development

Example:

// Set up a resource bundle message source
final messageSource = ResourceBundleMessageSource();
messageSource.setBasename('messages');
messageSource.setDefaultEncoding('UTF-8');
messageSource.setCacheSeconds(300); // Cache for 5 minutes

context.setMessageSource(messageSource);

// Usage in application components
class InternationalizedService {
  final MessageSource messageSource;
  
  InternationalizedService(this.messageSource);
  
  String getWelcomeMessage(String username, Locale locale) {
    return messageSource.getMessage(
      'welcome.message',
      args: [username],
      locale: locale,
      defaultMessage: 'Welcome, $username!'
    );
  }
}