Prepare subdomain registrar for Stacks 2.0

[markmhendrickson]

The registrar needs modification by the release of Stacks v2 so that sponsored ID registration either during onboarding or subsequently do not break.

[jcnelson]

I'm not sure anything on the public API side is going to change, but will let @kantai provide the details if not. I think the only major changes in the subdomain registrar are going to be in making sure it generates, broadcasts, and monitors the confirmations of Stacks v2 transactions.

[kantai]

Yep -- the API shouldn't need to change beyond a field or two.

The status reporting API /v1/names/<subdomain>.<domain> will change because the last_txid field will no longer be a Bitcoin txid, but that's pretty much it.

The backend will need to change more dramatically though.

[markmhendrickson]

The latest thinking is that @hstove will take on this work once @lgalabru has modified the Stacks node to support all requisite changes.

[markmhendrickson]

@diwakergupta should we assign this to someone on the Tintash team?

[markmhendrickson]

Thanks everyone for your contributions to the update. 🙏