feat: added operator == and expand unit test for pendingAirdropld

[davin-core]

Description:

• added the declaration operator == in PendingAirdropId.h
• implement the operator ==comparing sender, reciver, FT and NFT fields in PendingAirdropId.cc
• added new tests for NFT fromProtobuf, equality (FT/NFT), and inequality cases (different sender/receiver/token) in PendingAirdropIdUnitTests.cc:

Fixes #1267

[github-actions]

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[gsstoykov]

I know this goes out of the issue scope but shouldn't we maintain the operator for more/all data holders? @rwalworth

[rwalworth]

LGTM - everything looks great here, @davin-core! The operator== implementation correctly compares all four member fields, and the new tests cover the full range of cases from the issue: NFT fromProtobuf, equality for both FT and NFT, and three distinct inequality scenarios. Running workflows and will merge once they pass!

[rwalworth]

I know this goes out of the issue scope but shouldn't we maintain the operator for more/all data holders? @rwalworth

Absolutely @gsstoykov! You're right that we should add operator== to the broader set of data holder types (info structs, transfer types, allowance types, receipt/record types, etc.). The ID types already have it, but there are quite a few value-like types that don't. I'll look to spawn a batch of issues to cover these systematically.