Ensure h2 Websocket requests include :scheme

[zarqman]

This PR causes :scheme to be properly populated for http2 Websocket requests.

:scheme is presently showing up to the server as an empty string (which is odd, since I'd expect it to be nil instead--I did not chase this down).

According to RFC 8441, section 4, bullet 2, :scheme must be present for h2 WS requests (which contrasts to other uses of h2 CONNECT, where :scheme is expected to be omitted).

This also adds tests for the presence and validity of authority, path, and protocol.

Types of Changes

• Bug fix.

Contribution

• I added tests for my changes.
• I tested my changes locally.
• I agree to the Developer's Certificate of Origin 1.1.

[ioquatix]

This looks okay to me, but realistically speaking, is there ever going to be a case where we want to override the scheme in this way? We can always introduce an argument later, but maybe we can use @delegate.scheme on line 100 for now? WDYT?

[zarqman]

I don't presently have a concrete use case for the extra arg. It does pass through from def self.connect(..., **options) on line 55, so it's a little more versatile than at first glance.

Because of that pass through, my intention was to parallel the usage of Async::HTTP::Client where high-level method calls already support overriding scheme: apart from the endpoint. If that parallelism seems worth it, then perhaps keep it? Otherwise, it's no problem to remove the arg. I'll let you make the call. 😄

[ioquatix]

Suggested change

	def connect(authority, path, scheme: @delegate.scheme, headers: nil, handler: Connection, extensions: ::Protocol::WebSocket::Extensions::Client.default, **options, &block)
	def connect(authority, path, headers: nil, handler: Connection, extensions: ::Protocol::WebSocket::Extensions::Client.default, **options, &block)
	scheme = @delegate.scheme