Add codegen option about convert enum case name strategy

[bannzai]

This pull request to release/1.0 branch. And related and depend on this PR: #2477

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See #2477 before this PR.

Abstract

I use apollo-ios codegen version of v1-beta3. My service provide UPPER_CASE enum schema. It will genarate to case UPPER_CASE, but It was no good syntax in swift.
Therefore, I create about proposal PR of add to codegen option about enum case convert strategy. I would find a good form through this PR for generating enum case name.

Test

I confirmed to behavior with executing codegen script in my local. And Run UnitTests are passed.

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[AnthonyMDev]

Thanks so much for the PRs! I like this approach a lot and we've actually discussed doing something similar. I think we may want to consider utilizing this case conversion strategy option for other things like fields and type names, not just enum cases.

We'll have a conversation about this next week and decide on a direction here.

[AnthonyMDev]

We've decided that we are going to go ahead with this approach with a few minor changes! Thanks for making the PR @bannzai.

We want to change the naming from ConvertStrategy to ConversionStrategies.

Additionally, to support future use cases where we may add conversion strategies for other things, we want to refactor the configuration option to a struct that has a property for enumCases.

  public enum CaseConversionStrategy: String, Codable, Equatable {
    /// Default. Nothing different from the definition of a schema.
    case none
    /// Convert to lower camel case from `snake_case`, `UpperCamelCase`,`UPPERCASE`.
    case camelCase
  }

  public struct ConversionStrategies: Codable, Equatable {
    public let enumCases: CaseConversionStrategy = .camelCase
  }

I'm leaning towards defaulting to .camelCase instead of .none, here. @calvincestari what do you think?

@bannzai Do you want to make these changes to the PR so we can merge it in, or would you like me to do so and make a new PR?

[bannzai]

@AnthonyMDev I will try it!

[calvincestari]

I'm leaning towards defaulting to .camelCase instead of .none, here. @calvincestari what do you think?

.camelCase seems the most likely output that people would want in Swift code, I'm happy with that as the default.

[bannzai]

I'm done to replace new strctures and testing it. Ready for review!

[AnthonyMDev]

Thanks so much! This looks great!
Going to merge this in and then clean up the documentation a little bit.