The Mailgun provider was relying on an old behavior of
`ResourceData.Set` that would allow nested access to
maps. We now just build up our own maps like sane people.
Fixes the following vet report:
builtin/providers/mailgun/resource_mailgun_domain_test.go:73: arg DomainResp.Domain.Wildcard for printf verb %s of wrong type: bool
Before all providers were using the helper.Schema approach the helper
function had these names. Now they all use names consistent with the Go
naming conventions except for these last few…
Paul Hinze