Notes:

1. To confirm, we're talking about when developers are using the Test Kitchen SDKs and not the Event Platform SDKs?
2. We need to ensure that we support developers using custom streams and schemas

I figure the solution looks something like:

class Experiment {
  send( action, interactionData ) {
    // ...
    if ( event.action_context && typeof event.action_context !== 'string' ) {
      event.action_context = JSON.stringify( event.action_context );
    }
  }
}

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