Support for additional properties defined by Serverless plugin

[fredericbarthelet]

Original intent : add the serverless-step-functions plugin definition in #39

In order to implement definitions from https://github.com/serverless-operations/serverless-step-functions plugin within this package, one way could simply be to add dependency to this specific plugin in

typescript/serverless.yml

Lines 6 to 7 in b9825f6

	plugins:
	- ./dist/plugin

One downside of such implementation is the lack of constraint for this plugin to be referenced in your serverless.yml before being able to leverage definitions specifics to the plugin. Do you have any idea to enforce such behavior ?

✅ Validation with correct types

const serviceFile: AWS = {
  service: 'my-app'

  plugins: ['serverless-step-functions']

  // It's ok to write those properties as the plugin is referenced above
  stepFunctions: {
    stateMachines: //...
}

❌ Validation with incorrect types

const serviceFile: AWS = {
  service: 'my-app'

  plugins: ['another-plugin']

  // Should not allow those properties, as serverless-step-functions is not referenced in plugins property
  stepFunctions: {
    stateMachines: //...
}

[rsilvr]

For me it's a deal breaker that serverless.ts doesn't allow for custom definitions from plugins. In my case, I need to use the warmup proprerty in the function level (from serverless-warmup-plugin)

But I'll keep one eye on this. Using code instead of yaml it's a great proposition!

[julbr]

same issue for me with warmup plugin.