allow emit override

[williamkapke]

I want to customize the data that is emitted.

Example:

var handler = require('github-webhook-handler')({
  path: '/github',
  secret: 'hush-hush',
  emit: (headers, data)=> {
    data.custom = "I'm special";
    handler.emit(headers['x-github-event'], data);
  }
});

[rvagg]

I think I'd rather encourage either intermediate EventEmitters or emitting custom events back on the original.

e.g.

var handler = require('github-webhook-handler')({ ... })
var EE = require('event').EventEmitter()
var intermediate = new EE()

handler.on('whatever', (data) => { data.foo='bar'; intermediate.emit('somethingElse', data)) })

// use `intermediate` where you need

or

var handler = require('github-webhook-handler')({ ... })

handler.on('whatever', (data) => { data.foo='bar'; handler.emit('somethingElse', data)) })

Is there a scenario that either of these doesn't handle properly?

[williamkapke]

The 1st option is so hacky! A simple option like this PR (2 lines of code) allows people to customize at the heart of it. If I'm going to use my own EE, that eliminates 1/3 of the role of this module.

The 2nd option doesn't offer a great path if someone wants to massively change the data (like remove things) or just cancel/ignoring events altogether.

[williamkapke]

Needed to go a different direction after all 🍻