Add support for avoiding shifts on specific dates with reasons

rota_generator/workers.py

@@ -117,6 +117,7 @@ class AvoidShiftOnDates(BaseModel):
     start_date: Optional[datetime.date] = None
     end_date: Optional[datetime.date] = None
     dates: Optional[list[datetime.date]] = None
+    reason: Optional[str] = None
 
     @field_validator("start_date", "end_date", mode="before")
     def coerce_dates(cls, v):
@@ -428,6 +429,7 @@ class Worker(BaseModel):
                     "start_date": av.start_date,
                     "end_date": av.end_date,
                     "dates": av.dates,
+                    "reason": getattr(av, "reason", None),
                 }
                 # append to rota-level list; the model builder will enforce these
                 if hasattr(Rota.constraint_options_model, "avoid_shifts_by_worker_dates"):