Add WebServiceHandler interface.

[mikkokar]

Summary

Adds a new interface WebServiceHandler into Styx API.

It is a handler for HTTP static HTTP requests, useful for implementing "web service" endpoints with fixed content payload.

This prevents unintended errors where live HTTP message bodies are not properly consumed, and thus leaving the underlying TCP connection engaged.

Other changes are:

• Refactor MetricsHandler
• Convert admin interface endpoints to implement WebServiceHandler
• Adapters for bridging between WebServiceHandler and HttpHandler interfaces

[kvosper]

Many classes, including some tests, have methods unnecessarily reordered. My comment ask for them to be put back into the correct places.

I will review the code properly after this is done.

[dvlato]

I don´t know if this "Web service" describes the functionality correctly. The handler does not have to be used to implement web services, and a webservice might need to stream the body of the request. I guess we should describe that´s a handler that works in a non-streaming fashion.

However I am also wondering if this is the best way to fix the issue... couldn´t it appear in cases in which we cannot use a WebserviceHandler?

[mikkokar]

Hi @dvlato.

• I'm not 100% happy with this name either. Seems contrived. However it hints at most likely usage: web service endpoints which usually deal with finite sized objects. Should we consider naming it to StaticHttpHandler or something similar? WDYT?

• You are correct. There are cases where an HttpRequest can trigger a streaming LiveHttpRequest, and this interface won't help there. However being pragmatic, just look at our admin interface. This new interface caters for pretty every admin interface use case. Also going forward we need to improve the bridging between HttpHandler and WebServiceHandler. Please share any other ideas :-)

• Also worth noticing I'm not attempting to solve every content body issue in this PR. Just trying getting the admin interface (low hanging fruit) sorted. I still need to do more follow on work to cover the rest.

[dvlato]

StaticHttpHandler could be ok in this case.