Should be able to `Decode()` any supported signer/verifier agnostically

[Peeja]

Any principal.Signer or principal.Verifier can be Encode()d polymorphically, returning a multiformat value. But that value can't be re-Decode()d back to the correct implementation automatically, even though the multiformat contains enough information to select the implementation.

This has already been implemented locally in guppy, but the implementation properly belongs in go-ucanto.

[alanshaw]

This is a ComposedDIDParser in JS Ucanto https://github.com/storacha/ucanto/blob/3eb6a632b284a2762ce9c7bced27c49023744558/packages/principal/src/verifier.js#L3-L52

Please open the PR 🙏

[hannahhoward]

This issue has been automatically moved to Stuck / Dead Issue status.

Reason: No activity for 191 days (threshold: 180 days)

If this issue is still relevant and you'd like to work on it, please:

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