[Proposal] Pure StepFunction

[claudiopastorini]

Similar to the Pure Lambda's Chalice support I propose to think about a new way to generate Step Functions through Domovoi.

I think that one big limit now is to support only one Step Function for a project. Another limit is that you cannot deploy a Step Function with all Resources defined somewhere (maybe through another Chalice project with @app.lambda_function() decorator).

In order to resolve these problems, I started to think about a new decorator that allows to generate a Step Function by only the state machine definition returned by it.

@app.step_function(state_machine_name="register-user")
def register():
    return REGISTER_USER_STEP_FUNCTION_DEFINITON

The step_function() decorator accepts one arg, an optional state_machine_name parameter if you don't want to use the python function name (very similar to the @app.lambda_function()) as Step Function name.

When you deploy the project Domovoi will create a new Step Function with the name {appname}-{stage}-{step_function_name}.

Doing this will allow us to define more than one Step Function inside the same project.

The step_function_task() decorator will remain but it will accept now another optional state_machine_name parameter that allow the user to give a name to the Step Function, if not provided will be used only the name {appname}-{stage}. You will be able to use both the step_function() and step_function_task() using the same step_function_name.

I started to work on it because I discovered the power of the Step Function and I want to be able to improve the performance of my already defined APIs using Chalice route() and lambda_function() decorators.

See #13