fix: merge feature flags with returned values from API to enrich flag availability in config

[estephinson]

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Summary

• Ensures feature flags that have been returned by the API are available within the context of netlify-config

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[eduardoboucas]

Can we add some tests?

[estephinson]

Can we add some tests?

I can't see an easy path to getting tests around this.

I've refactored to move the logic into getSiteInfo, but will be adding a single unit test to assert on that

[eduardoboucas]

I can see that asserting on the feature flags is a bit challenging given the current setup. I think it would be nice to get some tests on this area, because if we introduce a regression that stops certain feature flags from being surfaced, that can quickly become a super tricky problem to troubleshoot.

That's a bigger lift though, so it doesn't have to be part of this PR.

[eduardoboucas]

I don't think you need this fallback?

Suggested change

	const featureFlags = { ...passedFeatureFlags, ...(siteInfo.feature_flags ?? {}) }
	const featureFlags = { ...passedFeatureFlags, ...siteInfo.feature_flags }