[.locker] Add Signature Check In Mint Function

[setzeus]

Description

A story part in a epic for the main mint function found in (issue tbd), this particular issue revolves around verifying the signature sent from the admin principal when minting a new name.

An example provided by @hstove can be found here: https://explorer.hiro.so/txid/0x706833c15e8224ce5ca65394f8c63545ef47af0fe248dffd48e17f01a11e86fe?chain=testnet

User Stories

• Contract can verify a correctly-formatted signature

Action Items

• [ ] Implement the logic required for consuming an admin-side name registration

Open Questions