Inflate sets some basic parameters on the problem, mostly the type for now.

MakeInvalidFieldProblem is a helper function to make a BadRequest with extras.

RegisterError records an error -> P mapping, allowing the app to register specific errors that may occur in other packages to be rendered as a specific P instance.

Render writes a http response to `w`, compliant with the "Problem Details for HTTP APIs" RFC: https://tools.ietf.org/html/draft-ietf-appsawg-http-problem-00 `p` is the problem, which may be either a concrete P struct, an implementor of the `HasProblem` interface, or an error.

BadRequest is a well-known problem type.

NotFound is a well-known problem type.

ServerError is a well-known problem type.

P is a struct that represents an error response to be rendered to a connected client.

HasProblem types can be transformed into a problem.