refactor timeslot API filters

This MR:

• removes default values for start and end filter (see #189 (closed))
• renames start to startsAfter and end to endsBefore
• adds datetime support to startsAfter and endsBefore
• adds new datetime filter startsBefore and endsAfter

program/filters.py

@@ -184,22 +184,13 @@ class TimeSlotFilterSet(filters.FilterSet):
             "If specified without a datetime value the current date and time is assumed."
         ),
     )
-    # The start/end filters will always be applied even if no query parameter has been set.
-    # This is because we enforce a value in the clean_start and clean_end methods
-    # of the filterset form.
     start = filters.DateFilter(
         method="filter_start",
-        help_text=(
-            "Only returns timeslots after that start on or after the specified date. "
-            "By default, this is set to the current date."
-        ),
+        help_text="Only returns timeslots that start at or after the specified datetime.",
     )
     end = filters.DateFilter(
         method="filter_end",
-        help_text=(
-            "Only returns timeslots that end on or before the specified date. "
-            "By default, this is set to value of the start filter + 60 days."
-        ),
+        help_text="Only returns timeslots that end before the specified datetime.",
     )
 
     schedule_ids = IntegerInFilter(
@@ -242,26 +233,6 @@ class TimeSlotFilterSet(filters.FilterSet):
             queryset = self.filter_surrounding(queryset, "surrounding", timezone.now())
         return queryset
 
-    def get_form_class(self):
-        form_cls = super().get_form_class()
-
-        class TimeSlotFilterSetFormWithDefaults(form_cls):
-            def clean_start(self):
-                start = self.cleaned_data.get("start", None)
-                return start or timezone.now().date()
-
-            def clean_end(self):
-                end = self.cleaned_data.get("end", None)
-                return end or self.cleaned_data["start"] + datetime.timedelta(days=60)
-
-        # We only want defaults to apply in the context of the list action.
-        # When accessing individual timeslots we don’t want the queryset to be restricted
-        # to the default range of 60 days as get_object would yield a 404 otherwise.
-        if self.request.parser_context["view"].action == "list":
-            return TimeSlotFilterSetFormWithDefaults
-        else:
-            return form_cls
-
     class Meta:
         model = models.TimeSlot
         fields = [