Run a sitespeed check for arbitrary url passed POST in to an endpoint.

[mrchrisadams]

We want to make it possible to run a sitespeed check as a service, but we want to make it scale to zero using as open and green a stack as possible.

To begin with, we're using google cloud run, because:

• it works with containers which a v popular
• runs on knative, meaning we're not locking ourselves too much into one company
• it scales to zero
• there's a bunch of decent instrumentation and billing already set up.

To begin with, greenspeed needs to run as a service where it will accept a POST with data sent along the lines of this handler.

https://cloud.google.com/run/docs/tutorials/pubsub#run_pubsub_handler-nodejs

If this is a valid url, we pass the url to sitespeed with the following parameters:

./bin/sitespeed.js https://PROVIDED_URL --headless -n 1 --sustainable.enable  --sustainable.co2PerDomain --sustainable.dirtiestResources  --sustainable.pageViews 1000000 --

### Acceptance criteria

We can close this issue when we have a HTTP service that:

• accepts a url
• checks that it's valid
• runs sitespeed if valid