Issue Summary

Forge UI modules like bitbucket:repoMainMenuPage can be used in apps to extend the UI of Bitbucket. When installed in a workspace, these modules currently don't support access by users that aren't a part of the workspace as is the case with public repositories. Add support for these to work for such users in public repositories. 

Steps to Reproduce

1. Install a Forge app in a workspace with bitbucket:repoMainMenuPage module.
2. Visit a repo in the workspace that's marked as public, while logged in as a user that's not a member of the workspace.
3. Visit the menu page of the app in the public repo on the left nav.

Expected Results

The module page loads - the left navigation pane is visible with the new page displaying content as expected

Actual Results

The module page loads - the left navigation pane is visible with the new page not displaying anything. There are 403s and 404s noted in the XHR logs in developer console.

Workaround

Currently there is no known workaround for this behaviour. A workaround will be added here when available