add water history data

src/ems_water_grp/backfill_water_pg_1day.py

@@ -140,6 +140,10 @@ def quantize_3(value: Decimal) -> Decimal:
     return value.quantize(Decimal("0.001"), rounding=ROUND_HALF_UP)
 
 
+def non_negative(value: Decimal) -> Decimal:
+    return value if value >= 0 else Decimal("0")
+
+
 def normalize_items(items: List[dict]) -> List[Tuple[pendulum.DateTime, Decimal]]:
     points = []
     for item in items:
@@ -396,6 +400,7 @@ class WaterPgDailyBackfill:
                     sum((value for _, value in points), Decimal("0"))
                     / Decimal(len(points))
                 )
+                avg_value = non_negative(avg_value)
                 pg_rows.append((
                     device["device_id"],
                     device["mtid"],
@@ -406,7 +411,7 @@ class WaterPgDailyBackfill:
                     read_time_str,
                 ))
             else:
-                water_vol = last_value - first_value
+                water_vol = non_negative(last_value - first_value)
                 water_rows.append((
                     device["device_id"],
                     device["mtid"],