Studio Explorer Boilerplate HTML

[abernix]

Requirements

This replaces the behavior of redirecting directly to studio with the more complete implementation which includes a landing-page that is served locally and offers a redirect to Studio. This will match the behavior of Apollo Server and Apollo Gateway today, exactly. This offers more transparency to the user to understand what about to happen (the redirect) and allows them to optionally make the behavior sticky (on account of a browser cookie) for future requests.

• Rather than redirect on the Router's configured endpoint, this replaces that redirect with serving of HTML boilerplate (e.g., with content-type: text/html) when the appropriate accept header with a satisfying text/html value is met.
• Renders the same boilerplate HTML that Apollo Server uses, which the implementation for should be found here

Effectively, this should produce this experience:

Will Resolve #380