Issue Summary

Currently in Forge, when an event is triggered: Confluence events, the siteUrl is not included in the event payload. In Connect, we were able to retrieve the siteUrl using hostUser.getHost().getBaseUrl().

Steps to Reproduce

1. Trigger Forge events from https://developer.atlassian.com/platform/forge/events-reference/product_events/
2. None of them will return the siteUrl on the event payload.

Expected Results

As this feature exists in Connect, and we are ending Connect support, it would be better to have feature parity in Forge. 

Actual Results

No URL is returned in the payload.

Workaround

Before or after an event trigger, the URL can be fetched using the serverInfo endpoint and stored in a temporary variable to be used within the app's event context.

Endpoint: https://developer.atlassian.com/cloud/jira/platform/rest/v3/api-group-server-info/#api-rest-api-3-serverinfo-get