Improve trusted publishing error message (#11389)

Author: marcoieni

src/controllers/krate/publish.rs

@@ -164,7 +164,9 @@ pub async fn publish(app: AppState, req: Parts, body: Body) -> AppResult<Json<Go
 
     let auth = if let Some(trustpub_token) = trustpub_token {
         let Some(existing_crate) = &existing_crate else {
-            let error = forbidden("Trusted Publishing tokens do not support creating new crates");
+            let error = forbidden(
+                "Trusted Publishing tokens do not support creating new crates. Publish the crate manually, first",
+            );
             return Err(error);
         };
 

src/tests/krate/publish/trustpub.rs

@@ -297,7 +297,7 @@ async fn test_non_existent_token_with_new_crate() -> anyhow::Result<()> {
     let pb = PublishBuilder::new("foo", "1.0.0");
     let response = oidc_token_client.publish_crate(pb).await;
     assert_snapshot!(response.status(), @"403 Forbidden");
-    assert_snapshot!(response.text(), @r#"{"errors":[{"detail":"Trusted Publishing tokens do not support creating new crates"}]}"#);
+    assert_snapshot!(response.text(), @r#"{"errors":[{"detail":"Trusted Publishing tokens do not support creating new crates. Publish the crate manually, first"}]}"#);
 
     Ok(())
 }