Use RC API key for local development from local.xcconfig

[ajpallares]

Motivation

When using the testing apps for developing the SDK, we usually need to add our own RevenueCat API key and/or Proxy URL. However, before this PR:

• Each testing app had a different place where the API key and Proxy URL needed to be added
• We often committed, by mistake, the changes that contained the API keys, which was not critical, but still undesired

Description

This PR addresses the two pain points mentioned above when setting an API key for local development (or Proxy URL):

• Centralizes the place where the RevenueCat API key and Proxy URL are set for local development in the local.xcconfig file
• Because the local.xcconfig file is ignored by git in this repo, we can finally stop worrying about committing the API key by mistake

Notes

• The implementation for this relies on adding the local API key and Proxy URL to the info.plist of the projects, to make them available for the code to access.
• The CI for PaywallsTester app still relies on the existing implementation of replacing the value of the apiKey String in ConfigItem.swift

[JayShortway]

Yessss omg thank you! This was one of my main motivations for adding the Local.xcconfig file, but I hadn't gotten around to it yet. ❤️

I have some suggestions to take it even further haha.

[JayShortway]

Can we not get rid of all of these files, so we can get rid of the entire verify_no_included_apikeys() check?

[ajpallares]

Well I see the utility of having then in the sense that someone might forget about the local.xcconfig file thing and perhaps wants to do a quick change of the API key and they do it in the code directly. So it does not harm. That said, by that argument, I'd need to add the ConfigItem.swift file to it 😄

[JayShortway]

What do you think about removing this file and making the CI script create a Local.xcconfig file instead?

[ajpallares]

Well, this file is still needed for the PaywallsTester app. I mean, not needed per se, but it's good to have a centralized place where we get the necessary variables from the info.plist.

Regarding having the CI script create a Local.xcconfig, I think that could totally work, yes. I'll open a separate PR for the CI changes related to this one 👍

[JayShortway]

(This comment has nothing to do with the line it's attached to 😅)

We also have a :replace_api_key_integration_tests Fastlane lane. We could refactor that to write values to Local.xcconfig as well, instead of to the various files listed in that lane. Just a suggestion and definitely not a blocker for this PR, as that is not really a pain point for local development.

[ajpallares]

I see. But it would definitely be much cleaner. I'll do this in a separate PR for CI-related stuff. Thank you for the suggestions!!!

[aboedo]

YESSS

[ajpallares]

Related PR, but for Examples apps --> #4796

[tonidero]

This is great! 🫶

[facumenzella]

nit

Suggested change

	struct ConfigItem {
	enum ConfigItem {

[facumenzella]

lovely