core: replace policies with ids in ContractDefinition

[ndr-brt]

What this PR changes/adds

Replace the fields accessPolicy and contractPolicy with accessPolicyId and contractPolicyId on ContractDefinition, and inject PolicyStore to ContractDefinitionServiceImpl, ContractValidationServiceImpl and ContractOfferServiceImpl

Why it does that

Because policies are stored separately from contract definitions and they can be referenced by their id

Further notes

• removed NullAssetIndex as its use was impossible to reach.
• probably data-loader-cli needs further work but seemed too much for this PR. Since data-management api is in place is it still useful?

Linked Issue(s)

Closes #1137
Part 3. of #828

Checklist

• added appropriate tests?
• performed checkstyle check locally?
• added/updated copyright headers?
• documented public classes/methods?
• added/updated relevant documentation?
• added relevant details to the changelog? (skip with label no-changelog)
• formatted title correctly? (take a look at the CONTRIBUTING and styleguide for details)

[codecov-commenter]

Codecov Report

Merging #1144 (89773f3) into main (24956ec) will increase coverage by 0.13%.
The diff coverage is 88.75%.

@@             Coverage Diff              @@
##               main    #1144      +/-   ##
============================================
+ Coverage     62.63%   62.76%   +0.13%     
- Complexity     2973     2978       +5     
============================================
  Files           694      693       -1     
  Lines         15420    15406      -14     
  Branches       1043     1040       -3     
============================================
+ Hits           9658     9670      +12     
+ Misses         5332     5307      -25     
+ Partials        430      429       -1     

Impacted Files	Coverage Δ
...ceconnector/contract/ContractServiceExtension.java	0.00% <0.00%> (ø)
...ion/store/SqlContractDefinitionStoreExtension.java	0.00% <0.00%> (ø)
...ypes/domain/contract/offer/ContractDefinition.java	80.76% <60.00%> (+25.50%)	⬆️
...ract/validation/ContractValidationServiceImpl.java	60.78% <90.90%> (+2.45%)	⬆️
.../contract/offer/ContractDefinitionServiceImpl.java	100.00% <100.00%> (+4.76%)	⬆️
...ector/contract/offer/ContractOfferServiceImpl.java	100.00% <100.00%> (+10.52%)	⬆️
...tDefinitionDtoToContractDefinitionTransformer.java	100.00% <100.00%> (ø)
...tDefinitionToContractDefinitionDtoTransformer.java	100.00% <100.00%> (ø)
...tamanagement/policy/service/PolicyServiceImpl.java	87.09% <100.00%> (ø)
...definition/store/ContractDefinitionStatements.java	100.00% <100.00%> (ø)
... and 2 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 24956ec...89773f3. Read the comment docs.