Add some notes.
Add a test for Metadata.AsJSONBuffer.
Satisfy the test.
Add HTTP request helpers to the API client.
Drop a superfluous error return.
Add some doc comments.
Fix up a few error messages.
Use path.Join instead of fmt.Sprintf.
Drop support for insecure HTTP clients.
Add tests.
Add a doc comment.
GetHTTPClient -> NewHTTPClient.
Doer -> HTTPClient.
HandleHTTPFailure -> CheckHTTPResponse.
Simplify fake error handling.
Fix a doc comment.