feat(did creation route): reject unregistered did methods

[chumbert]

Change a small oversight in did creation admin route:

• Missing method parameter will default to sov
• Unknown (ie: not registed in DIDMethods) methods will be rejected

[swcurran]

This needs an update of the base-branch, please.

A question from a dummy looking at the code. It looks like the list of acceptable methods is kind of hard-coded (e.g. "SOV" in the code). Is there somewhere (that I'm missing) where there are other permitted methods, and a way to add more? Or is that not important in this context?

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

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[chumbert]

A question from a dummy looking at the code. It looks like the list of acceptable methods is kind of hard-coded (e.g. "SOV" in the code). Is there somewhere (that I'm missing) where there are other permitted methods, and a way to add more? Or is that not important in this context?

A very good question. Within ACA-Py the methods are hardcoded and are SOV and KEY.

However, ACA-Py provides DIDMethods, a registry of supported DID methods. Plugins can use this registry to register additional methods.

With this PR, the did creation endpoint checks the request method against the content of DIDMethods and rejects unknown methods. Without this PR, the endpoint would default any unknown method to SOV.