Support custom logicalId separate from name

[dougmoscrop]

I think it would be better to just use the key as the logical id, but this is more backwards-compatible.

This allows specifying an id that is different than the name. This makes it more deterministic for purposes of Ref, etc.

stepFunctions:
  stateMachines:
    foo:
      id: MyStateMachine # this only needs to be unique within the template
      name: myStateMachine-${opt:stage} # this has to be unique across stages, etc.

In fact, where key means the stateMachines key for a given state machine, I think making the name default to "{service}-{key}-{stage}" and the logicalId to {Key}StepFunctionStateMachine is a very sensible default.

[horike37]

Hi, @dougmoscrop thank you for implementing such as the awesome enhancement 🎉
Just tested this PR and looks great to see working as expected 👍
I would love to add this to the next release!

Just one more thing, could you document the explanation of id statement to README?

[dougmoscrop]

Will do!

[dougmoscrop]

I updated the README and rebased on the latest changes.

[dougmoscrop]

@horike37 sorry for the delay, fixed the lint issues too. should be good to go.

[horike37]

@dougmoscrop
Thanks!