Move validation into form field.

src/pretix/base/forms/questions.py

@@ -90,7 +90,7 @@ from pretix.base.settings import (
     COUNTRIES_WITH_STATE_IN_ADDRESS, COUNTRY_STATE_LABEL,
     PERSON_NAME_SALUTATIONS, PERSON_NAME_SCHEMES, PERSON_NAME_TITLE_GROUPS,
 )
-from pretix.base.templatetags.rich_text import rich_text
+from pretix.base.templatetags.rich_text import rich_text, URL_RE
 from pretix.base.timemachine import time_machine_now
 from pretix.control.forms import (
     ExtFileField, ExtValidationMixin, SizeValidationMixin, SplitDateTimeField,
@@ -227,6 +227,11 @@ class NamePartsFormField(forms.MultiValueField):
                     # bots.
                     r'^[^$€/%§{}<>~]*$',
                     message=_('Please do not use special characters in names.')
+                ),
+                RegexValidator(
+                    URL_RE,
+                    inverse_match=True,
+                    message=_('Please do not use special characters in names.')
                 )
             ]
         }