Send valid payloads to Readme API

[JoelQ]

🧰 What's being changed?

This sends a valid hardcoded payload (in the form of the data.json file)
to the Readme API with all the proper headers and authentication.

The middleware now takes an API key during initialization and no longer
needs an endpoint which has become a constant.

The hard-coded data we wrote is valid according to HAR
1.2. We noticed that
there are some required fields from the spec that are neither mentioned
by the API nor used in the nodejs implementation. We decided to include
them for validity sake and at some point the backend might want to fully
support the HAR 1.2 spec.

The added fields are:

• entries.cache
• entries.timing
• entries[].request.cookies
• entries[].request.headerSize
• entries[].request.bodySize
• entries[].response.cookies
• entries[].response.headerSize
• entries[].response.bodySize
• entries[].response.redirectURL
• entries[].response.httpVersion

Some of these are empty arrays or objects but the keys are required to
be present.

As part of our development process, we introduced json-schema to check
the generated JSON we use (for now the static JSON file). We wrote a
schema file for the Readme.io-specific structure but were able to re-use
an existing implementation for the HAR
format.

🧪 Testing

There is an automated test the uses json-schema to guarantee the JSON is in the right format. We also manually tested this with the following Rack app:

$LOAD_PATH << File.expand_path("../path/to/metrics-sdks/packages/ruby/lib", __FILE__)
require "readme/metrics"

class ApiApp
  def call(env)
    puts "=== API ==="
    [200, {}, ["Ok"]]
  end
end

map "/api" do
  use Readme::Metrics, "YOUR_API_KEY_HERE"
  run ApiApp.new
end

run it on the command-line with:

$ rackup

Make a request:

$ curl http://localhost:9292/api/foo

then log into Readme.io dashboard and expect to see your request(s) there. Note that all the data will be from the hard-coded JSON file rather than actual data from the request.

[JoelQ]

Discussed IRL with @joshuaclayton, everything is good to go 👍