Added Renderable#data method to be able to respond with IO and String from an Action

[igor-alexandrov]

This PR closes #1219.

[jwoertink]

I think overall this looks great. I know several people have asked for something similar, so this will be a huge addition. I'm not familiar with sending data to the client like this, so the only thing I'm wondering is do we need to be concerned with sending too large of data, or any sort of weird security bugs like requesting with headers that should be disallowed? 🤷‍♂️

Other than that, just one small comment and it should be good to go 👍

[jwoertink]

Maybe we should also add an overload that takes HTTP::Status like the others? Just to keep those consistent.

[stephendolan]

@igor-alexandrov If you want to throw a couple code snippets of using this functionality into this PR, I'm happy to take those over to the website and help document the new feature if you haven't done so already.

[igor-alexandrov]

@stephendolan the most obvious example looks like:

class Reports::MyReport < ApiAction
  get "/reports/my_report" do
    result = CSV.build do |csv|
      csv.row "one", "two"
      csv.row "three"
    end

    data result, filename: "my_report.csv"
  end
end

Now I have doubts, do we really need data method that accepts IO or data with String first argument will be enough?
@jwoertink @paulcsmith what do you think?

[paulcsmith]

This looks great. I think just String probably makes sense since you can stringify an IO with to_s anyway.

Let me know when you've made the change and we can get this merged. Thanks so much!

[igor-alexandrov]

@paulcsmith done, I also added specs for "Content-Length" header.

[paulcsmith]

Looks great!