ChatMessage constructor
      
      ChatMessage({})
     
    
Creates a chat message containing either text or chatMedia, but not both.
// A text message:
final m1 = ChatMessage(text: 'Hello!', isSender: true);
// A media message:
final m2 = ChatMessage(
  chatMedia: ChatMedia(url: 'https://…', mediaType: MediaType.imageMediaType()),
  isSender: false,
);
Implementation
ChatMessage({
  required this.text,
  this.chatMedia,
  required this.isSender,
  this.createdAt,
});