Chat
    props:
      id<int>

  User
    props:
      id<int>
      chat<Chat>
      isAdmin<bool> - return true if user is admin of the group

    methods:
      send(text: string, [Choose]) - send PM to user. Really it is not useful due to bot can not initiate chat with user
      ban(duration: string) - ban user in group
      unban() - unban user. this would not readd user to the group (bot api does not support this action)
      capture(Event[]): <CaptureStop> - capture all next users messages in the messages group and begin to match them only against specified `Event list`

  Message
    props:
      raw - original data from API
      raw.message_id<int>
      user<User>
      chat<Chat>
      from<Message> - if message is a reply - it would contains previous message. TODO: rename it

    methods:
      send(text: string) - send new message to the messages channel
      reply(text: string) - send reply to the message
      remove() - remove message from channel

  Choose - abstraction for generating custom in-chat-buttons

TODO: refactor code to standalone module.

Example of rules:
'''js
    // Admin can ban user by replying to his\her massage with `\ban`. Works only if user is not admin.
    Reply('/ban')
        .then(async function( message ){
            if( (await message.user.isAdmin()) && !(await message.from.user.isAdmin())){
              message.from.reply(L('ban', {...message.from.user}));
              message.from.user.ban();
            }
        })
    Answer('/say {{$kokoko}}')
        .then((message, match)=>{
            message.send(match.kokoko)
        }),
'''