(PC-38798)[BO] feat: better format one-day datespan

Author: tpommellet-pass

api/src/pcapi/routes/backoffice/filters.py

@@ -297,10 +297,14 @@ def format_timespan(timespan: psycopg2.extras.DateTimeRange) -> str:
 def format_datespan(datespan: psycopg2.extras.DateRange) -> str:
     if not datespan:
         return ""
-    start = datespan.lower.strftime("%d/%m/%Y")
+    start_date = datespan.lower
+    start = start_date.strftime("%d/%m/%Y")
     if datespan.upper:
         # upper bound is exclusive, and we want to show the last day included in the date range
-        end = (datespan.upper - datetime.timedelta(days=1)).strftime("%d/%m/%Y")
+        end_date = datespan.upper - datetime.timedelta(days=1)
+        if start_date == end_date:
+            return start
+        end = end_date.strftime("%d/%m/%Y")
     else:
         end = "∞"
     return f"{start} → {end}"