Support self-hash value appearing in the subdomain

[vdods]

did:tdw supports DIDs whose "self certifying identifier" appears in the subdomain, e.g. did:tdw:{SCID}.example.com (see https://bcgov.github.io/trustdidweb/#method-specific-identifier).

did:webplus should be made to support this as well.

Comment: Because specification of subdomains involves modification of DNS records by the domain owner, it would be reasonable to consider a control over a subdomain-based did:webplus DID to imply control over the domain itself, and therefore could be considered to signify the identity of the VDR itself. This comment is not meant to necessarily establish that assumption in the did:webplus scheme.

[vdods]

A DID hosted on a domain whose subdomain was a self-hash would look pretty ugly/funny, something like did:webplus:uHiAWMBIHSLYAXMKwGvgFS7_T-C8F-iPsl6Co-7DxCpfqjA.example.com:uHiDX16BdTiK22Pog94gwSFNmB6rBOpfjtz3W0SYCT2e4IA

Probably only desired if it came with some stronger guarantees like the DID was also signed by the VDR's DID: did:webplus:uHiAWMBIHSLYAXMKwGvgFS7_T-C8F-iPsl6Co-7DxCpfqjA.example.com

Closing this as won't do for now, but could potentially address in the future.

[vdods]

Re-opening but marking as wontfix for now.