Event function source warning

[shettyvarun268]

This PR implements robust cross-region latency warnings within the Firebase Functions deployment pipeline to nudge developers away from unnecessary cross-region network hops. When an event-triggered function (such as Firestore or Cloud Storage) is explicitly assigned or defaults to us-central1 while its backing event resource operates in a distinct non-US location, the CLI now issues a user-friendly warning nudge encouraging explicit collocation with the event trigger's region. This validation integrates globally following Gen 2 EventArc trigger resolution, correctly handles US multi-region databases (such as nam5) to avoid false positives, and leaves deployment executions unblocked to prevent service disruptions.

[gemini-code-assist]

Code Review

This pull request refactors the Fabricator to manage invoker settings directly within the creation and update flows for Cloud Run functions, ensuring that null values explicitly set the invoker to public while undefined values preserve existing settings. Additionally, it adds a warning mechanism to alert users when a function in us-central1 is triggered by a resource in a different region. Feedback from the review highlights the need to exclude the us multi-region from these warnings to avoid false positives and suggests improving the warning message's guidance for multi-region triggers.

[gemini-code-assist]

The cross-region trigger validation should also exclude the us multi-region when the function is in us-central1. Similar to nam5 for Firestore, the us multi-region for Cloud Storage includes us-central1. Deploying a function in us-central1 to handle events from a us bucket does not constitute a cross-region hop, and flagging it would create false positives for many standard Storage-triggered functions.

      ep.eventTrigger.region !== "us-central1" &&
      ep.eventTrigger.region !== "nam5" &&
      ep.eventTrigger.region !== "us"

[gemini-code-assist]

The warning message suggests explicitly assigning the function to the trigger's region. However, for multi-region triggers (e.g., eur4, eu, asia), users cannot assign a function to that exact location as functions require a specific region. The advice should be refined to suggest a region within or closer to the multi-region to avoid guiding users toward an invalid configuration.

      const triggerRegion = ep.eventTrigger.region;
      const suggestion = triggerRegion.includes("-") ? triggerRegion : `a region within ${triggerRegion}`;
      utils.logLabeledWarning(
        "functions",
        `Function ${ep.id} located in us-central1 uses a trigger located in ${triggerRegion}. ` +
          `To avoid unnecessary cross-region network hops, you should explicitly assign this function to ${suggestion}.`,
      );