feat: new component for data models - DIDs, signatures, JSON-LD

[Moopli]

component/models/:

• did: afgo's DID and DID Doc models.
• ld: JSON-LD support - data models, context stores, LD-Proofs, canonicalization, etc.
• signature: signing APIs used in DID Docs etc.
• util: utility data models needed for other model implementations, but not specific to a given model.

[Moopli]

Comments are on #3565
PR was merged with a squash commit that had incorrect git metadata (commit message, authorship, signing, etc), this is fixed

[codecov]

Codecov Report

Merging #3568 (17ed66f) into main (3fd663d) will decrease coverage by 0.53%.
The diff coverage is 54.03%.

@@            Coverage Diff             @@
##             main    #3568      +/-   ##
==========================================
- Coverage   87.76%   87.24%   -0.53%     
==========================================
  Files         351      353       +2     
  Lines       48627    48671      +44     
==========================================
- Hits        42677    42461     -216     
- Misses       4402     4673     +271     
+ Partials     1548     1537      -11     

Impacted Files	Coverage Δ
component/models/did/endpoint/endpoint.go	91.50% <ø> (ø)
component/models/did/helpers.go	54.47% <ø> (ø)
component/models/did/legacy.go	92.94% <ø> (ø)
component/models/did/serialize_default.go	100.00% <ø> (ø)
...ponent/models/ld/context/remote/remote_provider.go	79.48% <ø> (ø)
component/models/ld/proof/utils.go	78.84% <ø> (ø)
component/models/ld/store/context_store.go	87.50% <ø> (ø)
component/models/ld/store/remote_provider_store.go	93.87% <ø> (ø)
...e/suite/bbsblssignature2020/public_key_verifier.go	100.00% <ø> (ø)
...te/bbsblssignatureproof2020/public_key_verifier.go	100.00% <ø> (ø)
... and 39 more