Override feature flags #649

Problem Statement

The docs mention the ability to override feature flags through the SDK, but it’s only available for web and react native.

• Flutter (Override feature flags posthog-flutter#180)
• Android (Override feature flags posthog-android#564)
• iOS (this issue)
• RN

Solution Brainstorm

It would be great to have the feature available on flutter, as it would make testing much easier if we can allow individuals to control the flags directly from the frontend.