added price drops to alerts/fixed race condition where late claimed docs got their tags wiped and sent to the api without tags

src/monitor_utils/database.py

@@ -282,16 +282,19 @@ def extract_recorded_prices(existing_doc: dict | None) -> set[float]:
 def build_alert(monitor_name: str, document: dict, now: datetime) -> dict:
     """Build an alert referencing a product for consumer delivery.
 
-    The alert carries its own copy of the document's newListing flag: the
-    product doc is rewritten every cycle, so its flag flips False one cycle
-    after discovery, while a discovery alert may sit in a backed-up queue
-    longer than that. The alert's copy is written once and cannot rot.
+    The alert carries its own copy of the document's newListing flag and
+    priceBeforeDrop: the product doc is rewritten every cycle, so its flag
+    flips False one cycle after discovery and its priceBeforeDrop is
+    cleared by the next cycle that sees no drop, while an alert may sit in
+    a backed-up queue longer than that. The alert's copies are written once
+    and cannot rot.
 
     Args:
         monitor_name: Monitor that produced the product, used by the
             consumer to resolve the owning collection and thresholds.
         document: Product document supplying the id, pricing for the
-            priority calculation, and the stamped newListing flag.
+            priority calculation, and the stamped newListing flag and
+            priceBeforeDrop.
         now: Detection timestamp stored as createdAt.
 
     Returns:
@@ -306,6 +309,7 @@ def build_alert(monitor_name: str, document: dict, now: datetime) -> dict:
         "attempts": 0,
         "createdAt": now,
         "newListing": document.get("newListing", False),
+        "priceBeforeDrop": document.get("priceBeforeDrop"),
     }