Field Merging[2/x] Compute MergedSelections w/MergingStrategy

[AnthonyMDev]

TL;DR

Updated the logic for merging selections in ComputedSelectionSet.

What changed?

• Implemented a new MergedSelections logic to handle different merging strategies.

How to test?

Unit tests will be written before this PR is marked ready for review.

Why make this change?

To improve the handling of merged selections in ComputedSelectionSet based on different merging strategies.

---

[AnthonyMDev]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
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• Deprecate localCacheMutation selectionSetInitializer option #350
• Field Merging [5/x] Move fieldMerging option to experimental #344
• Field Merging [4/x] Disable SelectionSetInitializers when field merging is enabled #343
• Field Merging [3/x] Implement in SelectionSetTemplate #318
• Field Merging[2/x] Compute MergedSelections w/MergingStrategy #307 👈
• Field Merging[1/x] Configuration Options #306
• Remove redundant iteration in EntitySelectionTree merging algorithm #308
• main

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[tahirmt]

@AnthonyMDev I ran this branch without field merging and I'm still seeing merged fields. I reproduced it on a sample project for easy review https://github.com/tahirmt/apollo-codegen-demo. Maybe I missed something but I think I got everything set up correctly.

Here fieldMerging is set to none
https://github.com/tahirmt/apollo-codegen-demo/blob/98b3390ecb0b35e3c4939176656f44442a90aab0/Sources/codegen/Command.swift#L31

And here is the generated query still showing merged fields
https://github.com/tahirmt/apollo-codegen-demo/blob/98b3390ecb0b35e3c4939176656f44442a90aab0/API/Sources/Operations/Queries/NodeQuery.graphql.swift#L60

Let me know if I missed anything

[AnthonyMDev]

I made a very silly oversight yesterday. While the field merging strategies work properly, they are not actually affecting the generated templates yet. I'm going to get that sorted out today and will have another PR up with this working soon!
Sorry for the confusion @tahirmt

[tahirmt]

Ah no worries. I was just too excited to try out.