dedupe keys on batch insert

api/src/database/records.rs

···
     async fn batch_insert_records_chunk(&self, records: &[Record]) -> Result<(), DatabaseError> {
         let mut tx = self.pool.begin().await?;
 
+        let mut deduped = std::collections::HashMap::new();
+        for record in records {
+            let key = (&record.uri, &record.slice_uri);
+            deduped.insert(key, record);
+        }
+        let records: Vec<&Record> = deduped.into_values().collect();
+
         let mut query = String::from(
             r#"INSERT INTO "record" ("uri", "cid", "did", "collection", "json", "indexed_at", "slice_uri") VALUES "#,
         );