Fix #978 -- Allow to split names (#1049)

- [x] attendee names
- [x] Invoice address names
- [x] Data migration
- [x] API serializers
  - [x] orderposition
  - [x] cartposition
  - [x] invoiceaddress
  - [x] checkinlistposition
- [x] position API search
- [x] invoice API search
- [x] business/individual required toggle
- [x] Split columns in CSV exports
- [x] ticket editor
- [x] shredder
- [x] ticket/invoice sample data
- [x] order search
- [x] Handle changed naming scheme
- [x] tests
- [x] make use in:
  - [x] Boabee
  - [x] Certificate download order
  - [x] Badge download order
  - [x] Ticket download order
- [x] Document new MySQL requirement
- [x] Plugins

src/pretix/presale/forms/checkout.py

@@ -66,7 +66,7 @@ class InvoiceNameForm(InvoiceAddressForm):
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         for f in list(self.fields.keys()):
-            if f != 'name':
+            if f != 'name_parts':
                 del self.fields[f]