feat: adds REST API for policy evaluation plan

[wolf4ood]

What this PR changes/adds

introduces an alpha REST API for policy evaluation plan.

Why it does that

Improve policies management and debuggability

Further notes

For example given this policy in MVD:

policy example

{
       "@id": "require-membership",
       "@type": "PolicyDefinition",
       "createdAt": 1725466366896,
       "policy": {
           "@id": "51d3c610-b141-4269-a4c0-df2a77122cfe",
           "@type": "odrl:Set",
           "odrl:permission": {
               "odrl:action": {
                   "@id": "use"
               },
               "odrl:constraint": {
                   "odrl:leftOperand": {
                       "@id": "MembershipCredential"
                   },
                   "odrl:operator": {
                       "@id": "odrl:eq"
                   },
                   "odrl:rightOperand": "active"
               }
           },
           "odrl:prohibition": [],
           "odrl:obligation": []
       },
       "@context": {
           "@vocab": "https://w3id.org/edc/v0.0.1/ns/",
           "edc": "https://w3id.org/edc/v0.0.1/ns/",
           "odrl": "http://www.w3.org/ns/odrl/2/"
       }
   },

An evaluation plan output within the catalog scope will look like this:

evaluation plan in catalog scope

{
    "@type": "PolicyEvaluationPlan",
    "preValidators": [],
    "permissionSteps": {
        "@type": "PermissionStep",
        "isFiltered": false,
        "filteringReasons": [],
        "ruleFunctionSteps": "ExamplePermissionFunction",
        "constraintSteps": {
            "@type": "AtomicConstraintStep",
            "isFiltered": false,
            "filteringReasons": [],
            "functionName": "MembershipCredentialEvaluationFunction",
            "functionParams": [
                "'MembershipCredential'",
                "EQ",
                "'active'"
            ]
        },
        "dutySteps": []
    },
    "prohibitionSteps": [],
    "obligationSteps": [],
    "postValidators": [],
    "@context": {
        "@vocab": "https://w3id.org/edc/v0.0.1/ns/",
        "edc": "https://w3id.org/edc/v0.0.1/ns/",
        "odrl": "http://www.w3.org/ns/odrl/2/"
    }
}

while in the request.catalog scope will look like this:

evaluation plan in catalog scope

{
    "@type": "PolicyEvaluationPlan",
    "preValidators": "DcpScopeExtractorFunction",
    "permissionSteps": {
        "@type": "PermissionStep",
        "isFiltered": false,
        "filteringReasons": [],
        "ruleFunctionSteps": [],
        "constraintSteps": {
            "@type": "AtomicConstraintStep",
            "isFiltered": true,
            "filteringReasons": [
                "leftOperand 'MembershipCredential' is not bound to scope 'request.catalog'",
                "leftOperand 'MembershipCredential' is not bound to any function within scope 'request.catalog'"
            ],
            "functionParams": [
                "'MembershipCredential'",
                "EQ",
                "'active'"
            ]
        },
        "dutySteps": []
    },
    "prohibitionSteps": [],
    "obligationSteps": [],
    "postValidators": "DefaultScopeMappingFunction",
    "@context": {
        "@vocab": "https://w3id.org/edc/v0.0.1/ns/",
        "edc": "https://w3id.org/edc/v0.0.1/ns/",
        "odrl": "http://www.w3.org/ns/odrl/2/"
    }
}

Linked Issue(s)

Closes #4447