[Idea] Support for DID Auth

[decentralgabe]

DID based authentication has been floating around for a few years, with a few varieties. It would be great to have a lightweight implementation we could use across applications.

References:

• https://github.com/WebOfTrustInfo/rwot6-santabarbara/blob/master/final-documents/did-auth.md
• https://www.w3.org/Security/201812-Auth-ID/04_-_Day_1_-_Understanding_DID_Auth.pdf