Prover: fix credx credential retrieval

[Patrik-Stas]

• Fixes retrieval of credentials for prover. When multiple restriction objects are specified, they should be treated as OR instead of AND. Verifier is asking prover to satisfy at least 1 restriction object, not all of them.

• Adds test test_agency_pool_it_should_select_credentials_for_satisfiable_restriction which was failing without modifications to WQL made in the PR. Passes with the modifications. See anoncreds spec https://hyperledger.github.io/anoncreds-spec/#restrictions

A boolean expression is formed by ORing and ANDing the source credential properties. The following JSON is an example. Any of the source credential properties listed above can be used in the expression components:

  "restrictions": [
    {
      "issuer_did": "<did>",
      "schema_id": "id"
    },
    {
      "cred_def_id" : "<id>",
      "attr::color::marker": "1",
      "attr::color::value" : "red"
    }
  ]

The properties in each list item are AND’d together, and the array elements are OR’d together. As such, the example above defines the logical expression:

The attributes must come from a source verifiable credential such that:
issuer_did = AND
schema_id =
OR
cred_def_id = AND
the credential must contain an attribute name "color" AND
the credential must contain an attribute name "color" with the attribute value "red"

• Test refactoring also uncovered that test test_agency_pool_it_should_fail_to_select_credentials_for_predicate is not working with credx implementation; see: Prover: support predicates for credx credential selection #962

[gmulhearn]

LGTM; but would be good to fix up my comment while you're in this area.

(Or consider the comment and let me know if there is something I'm not understanding)

Good to merge after that

[codecov-commenter]

Codecov Report

Merging #961 (ada6976) into main (f8aaadc) will decrease coverage by 0.12%.
The diff coverage is 77.55%.

@@            Coverage Diff             @@
##             main     #961      +/-   ##
==========================================
- Coverage   39.35%   39.23%   -0.12%     
==========================================
  Files         417      417              
  Lines       28986    28968      -18     
  Branches     6185     6187       +2     
==========================================
- Hits        11407    11367      -40     
- Misses      14236    14259      +23     
+ Partials     3343     3342       -1     

Flag	Coverage Δ
unittests-aries-vcx	39.23% <77.55%> (-0.12%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
...ries_vcx/src/handlers/proof_presentation/prover.rs	43.90% <0.00%> (-0.36%)	⬇️
aries_vcx_core/src/anoncreds/credx_anoncreds.rs	57.20% <63.63%> (-0.26%)	⬇️
aries_vcx/tests/test_creds_proofs.rs	88.31% <83.33%> (+0.07%)	⬆️
aries_vcx/tests/utils/scenarios.rs	83.11% <84.61%> (-0.36%)	⬇️

... and 5 files with indirect coverage changes

Lgtm

[gmulhearn]

Fix from my last comment looks good