`did:peer:4` integration, bugfix, improvements

[Patrik-Stas]

• Use did:peer:4 in didexchange (produce did:peer:4 in outgoing messages for both requester and responder)
  • Still supports counterparty using ptentially did:peer:2 (well, or any other DID method we support)

Additional updates:

• New get APIs for DidDocument:
  • assertion_method_by_key(&self, id: &str)
  • verification_method_by_id(&self, id: &str)
  • key_agreement_by_id(&self, id: &str)
  • capability_invocation_by_id(&self, id: &str)
  • capability_delegation_by_id(&self, id: &str)
• New update APIs for DidDocument, generally following pattern:
  • add_authentication(&mut self, method: VerificationMethodKind)
  • add_authentication_object(&mut self, method: VerificationMethod)
  • add_authentication_ref(&mut self, reference: DidUrl)

Fixes

• Fix bug on contextualize_to_did_doc which causes did:peer:4 to not fully decode

Error handling changes

• PeerDid<Numalgo4>::short_form(&self) does not return Result, but instead uses expect() which should never happens (see safety note in the code).
• DidPeer4ConstructionDidDocument::contextualize_to_did_doc(&self, did_peer_4: &PeerDid<Numalgo4>) is now also using panic upon conversion of DID type to URI type. Every DID is URI and therefore this should never panic. If panic occurs, it strictly indicates either:
  • buggy DID parsing (something that is not actually DID was parsed as a DID)
  • buggy URI parsing (something that is URI fails to be parsed as URI)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 141 lines in your changes are missing coverage. Please review.

Project coverage is 0.05%. Comparing base (09144f1) to head (20c48fa).

Files	Patch %	Lines
did_core/did_doc/src/schema/did_doc.rs	0.00%	70 Missing :warning:
...rc/protocols/did_exchange/state_machine/helpers.rs	0.00%	18 Missing :warning:
...peer_did/numalgos/numalgo4/construction_did_doc.rs	0.00%	15 Missing :warning:
aries/aries_vcx/tests/test_did_exchange.rs	0.00%	13 Missing :warning:
...ods/did_peer/src/peer_did/numalgos/numalgo4/mod.rs	0.00%	10 Missing :warning:
...change/state_machine/requester/request_sent/mod.rs	0.00%	9 Missing :warning:
...did_peer/src/peer_did/numalgos/numalgo2/helpers.rs	0.00%	4 Missing :warning:
...hange/state_machine/responder/response_sent/mod.rs	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1167 +/- ## ======================================== - Coverage 0.05% 0.05% -0.01% ======================================== Files 484 484 Lines 24184 24203 +19 Branches 4484 4490 +6 ======================================== Hits 13 13 - Misses 24171 24190 +19 ``` | [Flag](https://app.codecov.io/gh/hyperledger/aries-vcx/pull/1167/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=hyperledger) | Coverage Δ | | |---|---|---| | [unittests-aries-vcx](https://app.codecov.io/gh/hyperledger/aries-vcx/pull/1167/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=hyperledger) | `0.05% <0.00%> (-0.01%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=hyperledger#carryforward-flags-in-the-pull-request-comment) to find out more.

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