rework domain field

feeder-plugin/europepmc-feeder/src/europepmc.rs

@@ -301,7 +301,13 @@ fn into_discovery_record(r: EuropePmcResult, pmcid: String) -> DiscoveryRecord {
         fields.insert("title".to_string(), t);
     }
     fields.insert("fileType".to_string(), "document".to_string());
+    // `domain` travels with `contentKind` (METADATA_KEYS.md §1) — the key
+    // every client filters its wall on — and `workForm` travels with both. A
+    // paper stands alone. Stamped literally: this feeder pins the SDK by git
+    // tag and cannot reach `meta_feeder_sdk::domain`.
     fields.insert("contentKind".to_string(), "paper".to_string());
+    fields.insert("domain".to_string(), "science".to_string());
+    fields.insert("workForm".to_string(), "standalone".to_string());
     fields.insert(
         "sourceUrl".to_string(),
         format!("https://europepmc.org/article/PMC/{pmcid}"),