Add eventing for better access to bot execution.

[glossawy]

Looking to implement a small event architecture to enhance board commands.

The idea is that we could do something like:

bot.onCommandComplete(PingCommand.class, e -> e.success ? Boards.consume(e.userMessage) : somethingElse());

Commands would probably be:

• onCommandStart(Class<CommandBody>, Consumer<CommandStartEvent>)
  • Get command start events for this bot, but only ones initiated for the given Command class (e.g. PingCommand.class)
• onCommandStart(Consumer<CommandStartEvent>)
  • Get any command start events for this bot
• onCommandComplete(Class<CommandBody>, Consumer<CommandCompleteEvent>)
  • Get command complete events for this bot, but only ones initiated for the given Command class
• onCommandComplete(Consumer<CommandCompleteEvent>)
  • Get any command complete events

for now.

[glossawy]

No compelling use case