Custom parameter method

[sineed]

Related to #308

This PR add a method option that allows to use custom methods as a parameter value

For example:

post "/orders" do
  parameter :name, "Order name", required: true, method: :custom_name

  let(:custom_name) { "Custom order name" }

  ...
end

Also made some refactorings

[oestrich]

Thanks! I think this will fix a good deal of issues people have.

[rafaelsales]

@oestrich @sineed This fallback won't work for some scenarios.

Example:

get '/foo' do
  parameter :status, "Blah", method: :status_param # this param is not required

  example 'meh' do
    expect(status).to eq 200
  end
end

Even before entering the example block, rspec api documentation calls status to prepare the request, because status_param is not defined. When it calls status, it fails with No response yet. Request a page first, because the status method is only supposed to be called after a request is done.

I don't see a reason to have this fallback mechanism. If the programmer specifies a different method name for a param, just use it if present, if not, do not use the param at all.

[oestrich]

Your example is working as intended. If instead the example is an example_request then we hit your failure, which does exist. Status is a weird method to override, and we've always had an issue with it.

The problem line seems like it would be this one. I will look at a PR if you want to fix it, otherwise I don't see why you would change the method and not define it.

[rafaelsales]

@oestrich The status was just an example, but this issue happens to other reserved words on the context of a test example as well. I created a PR: #352
Thanks