Function parse_resource_arn 

pub fn parse_resource_arn(arn: &str) -> Option<(String, Option<String>)>

Parse an Amplify ResourceArn into (app_id, Option<branch>) for the tagging operations. Only apps and branches carry tags in the model.

• arn:aws:amplify:{region}:{account}:apps/{app_id} -> (app_id, None)
• .../apps/{app_id}/branches/{branch} -> (app_id, Some(branch))