Allow RelativeDate in relation to a moment of order (#6160)

* initial implementation

* factor out _resolve_base_date

* add js to prevent illegal inputs

* fix tests

* Update src/pretix/base/reldate.py

Co-authored-by: Raphael Michel <michel@pretix.eu>

* Apply suggestions from code review

Co-authored-by: Raphael Michel <mail@raphaelmichel.de>

* move js includes of to fragment_js.html

* add type annotations

* moves logic from RelativeDateWrapper into RelativeDate and adds BaseChoice for configuring which models attributes support which relationship

* fix tests

* test upgrade behaviour

* Apply suggestions from code review

Co-authored-by: Raphael Michel <mail@raphaelmichel.de>

* move reldate.js include in correct file

* add OptionAttrsSelect to allow select options with their own attributes per value

* add a little bit of information to the tests for future reference

* rewrite reldate.js use data-attributes

* general cleanup

* add test for order.subevents cases

* use correct choice format

* remove order.subevent variants

* various cleanup

* Apply suggestions from code review

Co-authored-by: Raphael Michel <mail@raphaelmichel.de>

* remove empty docstrings

* add depreciation warning

* change event listener to pretix:bind-forms

---------

Co-authored-by: Raphael Michel <michel@pretix.eu>
Co-authored-by: Raphael Michel <mail@raphaelmichel.de>

src/pretix/control/forms/subevents.py

@@ -94,14 +94,14 @@ class SubEventBulkForm(SubEventForm):
         label=_('Start of presale'),
         help_text=_('Optional. No products will be sold before this date.'),
         required=False,
-        limit_choices=('date_from', 'date_to'),
+        limit_choices=('event__date_from', 'event__date_to'),
     )
     rel_presale_end = RelativeDateTimeField(
         label=_('End of presale'),
         help_text=_('Optional. No products will be sold after this date. If you do not set this value, the presale '
                     'will end after the end date of your event.'),
         required=False,
-        limit_choices=('date_from', 'date_to'),
+        limit_choices=('event__date_from', 'event__date_to'),
     )
     skip_if_overlap = forms.BooleanField(
         label=pgettext_lazy('subevent', 'Skip dates that overlap with any existing date'),
@@ -333,12 +333,12 @@ class BulkSubEventItemForm(SubEventItemForm):
     rel_available_from = RelativeDateTimeField(
         label=_('Available from'),
         required=False,
-        limit_choices=('date_from', 'date_to'),
+        limit_choices=('event__date_from', 'event__date_to'),
     )
     rel_available_until = RelativeDateTimeField(
         label=_('Available until'),
         required=False,
-        limit_choices=('date_from', 'date_to'),
+        limit_choices=('event__date_from', 'event__date_to'),
     )
 
     def __init__(self, *args, **kwargs):
@@ -355,12 +355,12 @@ class BulkSubEventItemVariationForm(SubEventItemVariationForm):
     rel_available_from = RelativeDateTimeField(
         label=_('Available from'),
         required=False,
-        limit_choices=('date_from', 'date_to'),
+        limit_choices=('event__date_from', 'event__date_to'),
     )
     rel_available_until = RelativeDateTimeField(
         label=_('Available_until'),
         required=False,
-        limit_choices=('date_from', 'date_to'),
+        limit_choices=('event__date_from', 'event__date_to'),
     )
 
     def __init__(self, *args, **kwargs):