Phase 2: Add other HTTP helpers

[aleksa-krolls]

In Phase 1, we added a generic HTTP wrapper to OpenMRS called http.request, which allows arbitrary HTTP requests against the instanceUrl root.

As a logical extension of that, we want to add a few simple wrappers, with tests and documentation, for http.get(), http.post() and http.delete.

The new operations should include basic unit tests, along the lines of thee existing functionality.

See the http adaptor for a reference about what the APIs look like.

See parent issue #887 for details.

[martalovescoffee]

@hunterachieng could you please add an estimate to this issue?

[josephjclark]

Question: should we allow users to pass absolute URLs into these helpers? Can we do http.request('https://some-server.com')? If we do, it's important that we do not append OpenMRS credentials from state to the request.

The benefit of doing this is that we enable true generic HTTP through this adaptor. Users have to handle their own auth, if auth is needed.

This is actually generally discouraged - we tend to recommend creating a http step for this sort of thing.

Another reason not to do it is that it muddies the semantics of the http namespace. http.get() means "make an authorized request against the root instanceURL". If we allow absolute APIs then those semantics lose all meaning really.

[aleksa-krolls]

@josephjclark I think it's fine to assume that we're using the same credential for these and the root instanceUrl will be the same.

Agreed that if they want to make an http request to another API (not openmrs), then they should have another http step. The whole goal of this change is to enable users to send http requests to openmrs apis, not necessarily any api.