Closes #12988: Introduce custom field choice sets (#13195)

* Initial work on custom field choice sets

* Rename choices to extra_choices (prep for #12194)

* Remove CustomField.choices

* Add & update tests

* Clean up table columns

* Add order_alphanetically boolean for choice sets

* Introduce ArrayColumn for choice lists

* Show dependent custom fields on choice set view

* Update custom fields documentation

* Introduce ArrayWidget for more convenient editing of choices

* Incorporate PR feedback

* Misc cleanup

netbox/utilities/forms/widgets/misc.py

@@ -1,6 +1,7 @@
 from django import forms
 
 __all__ = (
+    'ArrayWidget',
     'ClearableFileInput',
     'MarkdownWidget',
     'NumberWithOptions',
@@ -43,3 +44,13 @@ class SlugWidget(forms.TextInput):
     Subclass TextInput and add a slug regeneration button next to the form field.
     """
     template_name = 'widgets/sluginput.html'
+
+
+class ArrayWidget(forms.Textarea):
+    """
+    Render each item of an array on a new line within a textarea for easy editing/
+    """
+    def format_value(self, value):
+        if value is None or not len(value):
+            return None
+        return '\n'.join(value)