Use UI to fill date into datetimepicker

This creates a new method to select date and time from datetimepicker.

Field cannot be filled "manually" (ie. by entering its value)

spec/features/admin/order_cycles/simple_spec.rb

@@ -462,8 +462,14 @@ feature '
       expect(page).to have_button('Create', disabled: false)
 
       # If I fill in the basic fields
-      fill_in 'order_cycle_orders_open_at', with: '2040-10-17 06:00:00'
-      fill_in 'order_cycle_orders_close_at', with: '2040-10-24 17:00:00'
+      find('#order_cycle_orders_open_at').click
+      select_datetime_from_datepicker Time.at(Time.zone.local(2040, 10, 17, 0o6, 0o0, 0o0))
+      # hide the datetimepicker
+      find("body").send_keys(:escape)
+      find('#order_cycle_orders_close_at').click
+      select_datetime_from_datepicker Time.at(Time.zone.local(2040, 10, 24, 17, 0o0, 0o0))
+      # hide the datetimepicker
+      find("body").send_keys(:escape)
       fill_in 'order_cycle_outgoing_exchange_0_pickup_instructions', with: 'pickup instructions'
 
       # Then my products / variants should already be selected

spec/support/features/datepicker_helper.rb

@@ -12,7 +12,15 @@ module Features
       navigate_datepicker_to_month date
       find('.flatpickr-calendar.open .flatpickr-days .flatpickr-day:not(.prevMonthDay)', text: date.strftime("%e").to_s.strip, exact_text: true, match: :first).click
     end
-    
+
+    def select_datetime_from_datepicker(datetime)
+      ## First of all select date
+      select_date_from_datepicker(datetime)
+      # Then select time
+      find(".flatpickr-calendar.open .flatpickr-hour").set datetime.strftime("%H").to_s.strip
+      find(".flatpickr-calendar.open .flatpickr-minute").set datetime.strftime("%M").to_s.strip
+    end
+
     def navigate_datepicker_to_month(date, reference_date = Time.zone.today)
       month_and_year = date.strftime("%-m %Y")