Checking ITruncatedCollecton.IsTruncated after enumeration. Fixes #1384

[uffelauesen]

This PR fixes #1384

The reading of ITruncatedCollection.IsTruncated (used by ODataResourceSetSerializer for nested resource sets) is postponed until after enumeration have completed.

This change is to support other implementations of ITruncatedCollection than the List based TruncatedCollection. Other implementations might not have the collection in memory when before enumeration starts and thus might not know if the data has been truncated like the List based one.

Some tests have been added - both my attempt to write a unittest with Mocks and an E2E test.

Copilot reviewed 5 out of 7 changed files in this pull request and generated no comments.

Files not reviewed (2)

• src/Microsoft.AspNetCore.OData/Formatter/Serialization/ODataResourceSetSerializer.cs: Evaluated as low risk
• test/Microsoft.AspNetCore.OData.Tests/Formatter/Serialization/SerializationTestsHelpers.cs: Evaluated as low risk

Comments suppressed due to low confidence (1)

test/Microsoft.AspNetCore.OData.E2E.Tests/ServerSidePaging/ServerSidePagingDataModel.cs:108

• The Dispose method is empty. If the class implements IDisposable, it should properly dispose of any unmanaged resources.

public void Dispose()