GraphQL: Add runningExperimentId in the Page Field

[rjvelazco]

Parent Issue

#30943

Task

When a page has an Experiment running, the Page API retrieves the runningExperimentId property. However, this property/field is currently inaccessible via GraphQL.

Proposed Objective

Same as Parent Issue

Proposed Priority

Priority 3 - Average

Acceptance Criteria

Preview Give feedback

1. Add the runningExperimentId property to the GraphQL schema.
2. Ensure the runningExperimentId is accessible when querying a page.

This QUERY should work:

query GetPageWithExperiment {
    page(url: "/test-with-experiments") {
        identifier
        title
        url
        runningExperimentId # Undefine field
    }
}