test: add policy-service coverage and related service tests

[mariana-andruk-qa]

Summary

Adds unit and contract test coverage for policy-service, plus a couple of related tests in guardian-service and api-gateway.

• policy-service: unit tests for block validators, blocks, helpers, decorators, errors, and policy-engine utilities, plus V8/c8 coverage tooling (run-coverage.mjs, coverage-report.mjs, COVERAGE_NOTES.md) and a block-about contract test.
• guardian-service: new build-documentation-urls helper with accompanying unit tests.
• api-gateway: dmrv service test (alias resolution) using esmock.

Test results

Run against freshly built dist/ output:

Service	Passing	Failing
api-gateway	12	0
guardian-service	16	0
policy-service	1254	0

The policy-service tests that were previously failing are now fixed:

• ORM-dependent validators no longer need a live database. schema-validator (and its property test) mock the ESM module via esmock.strict, and orchestrator-validators neutralises DatabaseServer reads on the real singleton instead of the non-working module mock. A .mocharc.json registers the esmock loader before mocha starts so the mock survives mocha's re-spawn.
• PolicyValidator argument mismatch: dropped the stray leading id argument so policy/isDryRun line up with the constructor signature.
• CommonBlock-delegating validators with mandatory options (TransformationUIAddon, HttpRequestUIAddon) now use per-block fixtures that supply the required fields.
• PolicyUtils expectations match the implementation: getDocumentType returns the DocumentType enum values (VerifiablePresentation/VerifiableCredential/DID) and DocumentSignature.NEW is numeric 0.

Notes

• yarn.lock changes were intentionally excluded (unrelated dependency churn).

[dariy-rised]

1. orchestrator-validators.test.mjs in @unit PolicyValidator
   Six tests call the constructor with a string 't-1' as the first argument.
   But the real constructor signature is:
   constructor(policy: Policy, isDruRun: boolean = false, ...) → 2 tests fail

Fix: remove 't-1'

2. orchestrator-validators.test.mjs and schema-validator.test.mjs: Module._load doesn't intercept ESM imports → ORM hits real DB → 3 tests fail

Fix: replace the Module._load block with esmock

3. policy-utils.test.mjs: getDocumentType returns enum strings, not 'vp-document', 'vc-document', 'did-document'.
   → 3 tests fail

Fix: update all three expected values to match the actual enum 'VerifiablePresentation', 'VerifiableCredential', 'DID'

4. policy-utils.test.mjs: DocumentSignature.NEW is numeric 0, not string 'NEW' → 2 tests fail

real enum is:

 export enum DocumentSignature {                                                                                                                                                                                
      NEW,      // = 0                                                                                                                                                                                         
      VERIFIED, // = 1
      INVALID,  // = 2
  }

Fix: replace 'NEW' to 0

5. common-only-validators-batch3.test.mjs: two validators require mandatory fields that the shared refOK fixture omits → 2 tests fail

TransformationUIAddon: requires options.expression
HttpRequestUIAddon: requires options.url and options.method

Fix: use per-block fixtures for the validators that have mandatory fields

6. also I have 13th test fail in http-request-block.test.mjs: IPv6 bracket handling bug
   This is the code bug and we will fix it soon.