HandleCreateDomainSuccessfully creates an HTTP handler at `/domains` on the test handler mux that tests domain creation.

HandleDeleteDomainSuccessfully creates an HTTP handler at `/domains` on the test handler mux that tests domain deletion.

HandleGetDomainSuccessfully creates an HTTP handler at `/domains` on the test handler mux that responds with a single domain.

HandleListDomainsSuccessfully creates an HTTP handler at `/domains` on the test handler mux that responds with a list of two domains.

HandleUpdateDomainSuccessfully creates an HTTP handler at `/domains` on the test handler mux that tests domain update.

CreateRequest provides the input to a Create request.

GetOutput provides a Get result.

ListOutput provides a single page of Domain results.

UpdateOutput provides an update result.

UpdateRequest provides the input to as Update request.

ExpectedDomainsSlice is the slice of domains expected to be returned from ListOutput.

FirstDomain is the first domain in the List request.

SecondDomain is the second domain in the List request.

SecondDomainUpdated is how SecondDomain should look after an Update.