Issue Summary:

When a Forge developer wants their app to open a URL with a custom scheme (for example - `someone@example.com`, `vscode://some.url/`, `spotify:track:abcd`), the required manifest changes should be:

// manifest.yml
modules:
  ...
resources:
 ...
permissions:
  external:
    fetch:
      client:
        - 'customscheme:*' 

If an app developer adds the above permissions block to their app, there is unintended behaviour in Jira Forge app installations.

Steps to Reproduce

1. Create and install a Forge app into a Confluence module as well as a Jira module
2. Enable custom scheme egress in the Forge app's manifest.yml (see code block above)
3. Create a button in the Forge app that redirects the app user to a URL with the allowed custom scheme
4. Attempt to interact with the app in the Jira module

Example app code that performs the above behaviour can be found here: ECO-1055.zip

Expected Results

The app user should be able to egress to a URL with a custom scheme, according to behaviour outlined in ECORFC-482 (internal document). The egress behaviour should be consistent across both Jira and Confluence.

Actual Results

The app user is able to egress to a URL with a custom scheme in Confluence. In Confluence, the behaviour aligns with ECORFC-482.

The app user is sometimes able to egress to a URL with a custom scheme in Jira. In Jirar, the behaviour does not align with ECORFC-482.

Workaround

The app developer may have to have some variation on the manifest.yml entry, for example:

// manifest.yml 
modules: 
... 
resources: 
... 
permissions: 
  external: 
    fetch: 
      client: 
        - address: 'customscheme://' # this does not align with ECORFC-482, may result in unexpected behaviour
        - address: 'customscheme:\\' # this aligns with ECORFC-482