Typed fields in route documentation blocks now broken with Sphinx 2.1.1

[ViktorHaag]

It seems like with the release of Sphinx v2.1.1, this domain's use of typed fields isn't really working any more in documentation where more than one domain gets used in the documentation.

Please see issue 6478 on Sphinx itself; I believe the defect lies in a refactoring that happened there, and not really here. A workaround fix for this domain package is to insert a _doc_field_type_map = {} class variable declaration inside the HTTPResource class definition, I think.