Bugfix: check to determine if asset can be deleted

[paullatzelsperger]

What this PR changes/adds

This PR adds a method to the ContractNegotiationStore that returns all ContractNegotiations that have a ContractAgreement which references a particular asset in order to check, whether the asset can be deleted or not.

Why it does that

Deleting Assets should be forbidden once it is referenced by a ContractAgreement. Previously the check used a filter expression, which is not (yet) implemented for SQL.

Further notes

• The implementations for CosmosDB and InMem did not change functionally - the same query as was there before can be used. Only SQL - due to its relational nature - needed some love.
• the ReflectionUtil threw a NPE when recursively resolving a field, who's parent is null, e.g. ContractNegotiation -> contractAgreement -> assetId when contractAgreement is null.

Linked Issue(s)

Closes #1403

Checklist

• added appropriate tests? (some)
• 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 #1408 (dbf03c4) into main (4a1cca9) will increase coverage by 0.00%.
The diff coverage is 80.00%.

@@           Coverage Diff           @@
##             main    #1408   +/-   ##
=======================================
  Coverage   67.60%   67.61%           
=======================================
  Files         719      719           
  Lines       15911    15928   +17     
  Branches     1043     1044    +1     
=======================================
+ Hits        10757    10770   +13     
- Misses       4678     4683    +5     
+ Partials      476      475    -1     

Impacted Files	Coverage Δ
...otiation/store/CosmosContractNegotiationStore.java	60.81% <0.00%> (-2.57%)	⬇️
...gotiation/store/ContractNegotiationStatements.java	96.42% <ø> (ø)
...negotiation/store/SqlContractNegotiationStore.java	81.72% <66.66%> (-0.51%)	⬇️
...aceconnector/common/reflection/ReflectionUtil.java	87.50% <100.00%> (+0.54%)	⬆️
...tiationstore/InMemoryContractNegotiationStore.java	90.47% <100.00%> (+2.14%)	⬆️
...datamanagement/asset/service/AssetServiceImpl.java	100.00% <100.00%> (ø)
.../contractnegotiation/store/PostgresStatements.java	89.18% <100.00%> (+1.68%)	⬆️

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