Proxy support in calling external API in Forge

We are building a Forge app for a data sync use case. We need to call an external API to get data. The user can configure a proxy URL with a username and password which we can call instead of the default URL mentioned in the manifest file. We are using fetch to call APIs.

Is it possible to set up a dynamic URL in the manifest file of the Forge app?
Is there any other way to set up a proxy URL with a username and password while calling the API?

You can use a wildcard in your egress permissions e.g.

permissions:
  external:
    fetch:
      backend:
        - '*'