code: func findAppPort(manifest *schema.PodManifest, portName types.ACName) (*types.Port, error) {
  	var foundPort *types.Port
  
  	for _, app := range manifest.Apps {
  		for _, port := range app.App.Ports {
  			if portName == port.Name {
  				if foundPort != nil { // error: ambiguous
  					return nil, fmt.Errorf("port name %q defined multiple apps", portName)
  				}
  				p := port // duplicate b/c port gets overwritten
  				foundPort = &p
  			}
  		}
  	}
  	return foundPort, nil
  }
docs: // findAppPort looks through the manifest to find a port with a given name.
  // If multiple apps expose the same port name, it will fail