Proposal: Consumer API

[maxlinc]

Here's my proposed API after playing around with some of the ideas on the roadmap. I think this idea will help tie together a lot of the items on the roadmap.

      # Simplest possible API
      Pacto.simulate_consumer do
        request 'create something'
      end

      # You should probably be able to use Contract objects instead of names, as well:
      contracts = Pacto.load_contract('my_contracts')
      Pacto.simulate_consumer do
        request contracts.first
      end

      # The use of named consumers will help with later reporting and CDC features
      Pacto.simulate_consumer :my_consumer do
        # Request should accept values for simulation
        request 'create something', color: 'blue', size: 'small'
        request 'create something', color: 'blue', size: 'large'
      end

      # You should also be able to pass the default values to the consumer, which
      # will be merged with values on the request. This has the same request as
      # the block above.
      Pacto.simulate_consumer :my_consumer, color: 'blue' do
        # Request should accept values for simulation
        request 'create something', size: 'small'
        request 'create something', size: 'large'
      end

      # We could add middlware to deal with the "enrichment" items on the roadmap
      Pacto.simulate_consumer :my_consumer, color: 'blue' do
        use CustomAuthentication
        use RandomHeaderCapitalization
        # ...
      end

      # The consumer should return a set of interactions
      interactions = Pacto.simulate_consumer :my_consumer, color: 'blue' do
        # Request should accept values for simulation
        request 'create something', size: 'small'
        request 'create something', size: 'large'
      end

      # We can probably add middleware to handle the "enrichment" items on the roadmap

      # This will clean up the RSpec API for collaboration testing. Previously we used
      # expect(Pacto).to ..., now you can do things like:

      # RSpec 3
      # expect(interactions).to include(an_interaction_for('create something').with(size: 'large'))

      # RSpec 2
      expect(interactions.first).to be_an_interaction_for('create something').with(size: 'large')

      # Interactions may also (in the future) have some aggregate methods or advanced capabilities, like:
      interactions.slowest(5) # returns the 5 slowest HTTP request/response interactions
      interactions.group_by(&:service) # groups by service, in this case 'create something'
      # auto_cleanup detects interactions that match a "creation pattern" (like a PUT, a
      # or a POST that returned a 201 (possibly as part of a POST-REDIRECT-GET), and sends
      # a DELETE request to undo the creation action.
      interactions.auto_cleanup

[maxlinc]

Created #144 for better interactions.

Need to fix to return interactions, then will close.