Calculate session expiry times in operations, using a common now timestamp for everything.

paskia/db/structs.py

@@ -309,7 +309,7 @@ class Session(msgspec.Struct, dict=True):
             "expiry": self.expiry.isoformat(),
         }
 
-    def store(self) -> None:
+    def store(self, now: datetime) -> None:
         """Store this session in the database and record a visit.
 
         Updates user.last_seen and user.visits. Must be called inside
@@ -317,7 +317,6 @@ class Session(msgspec.Struct, dict=True):
         """
         _data = db.data()
         _data.sessions[self.key] = self
-        now = datetime.now(UTC)
         _data.users[self.user_uuid].last_seen = now
         _data.users[self.user_uuid].visits += 1