Use AdminTinyMCE in the example app's admin pages.

The AdminTinyMCE widget is a slightly more opinionated version of the
TinyMCE widget, intended to look and behave slightly better when used
inside Django admin pages.

Additionally, add an admin interface for editing TestModel objects, to
allow testing the functionality of the HTMLField class (in the absence
of any custom ModelAdmin class.)

tests/testapp/admin.py

@@ -3,8 +3,8 @@
 from django.contrib.flatpages.models import FlatPage
 from django.urls import reverse
 
-from tests.testapp.models import TestInline, TestPage
-from tinymce.widgets import TinyMCE
+from tests.testapp.models import TestInline, TestModel, TestPage
+from tinymce.widgets import AdminTinyMCE
 
 
 class TinyMCETestInlineAdmin(admin.StackedInline):
@@ -14,7 +14,7 @@ class TinyMCETestInlineAdmin(admin.StackedInline):
     def formfield_for_dbfield(self, db_field, **kwargs):
         if db_field.name in ("content1", "content2"):
             return db_field.formfield(
-                widget=TinyMCE(
+                widget=AdminTinyMCE(
                     attrs={"cols": 80, "rows": 30},
                     mce_attrs={"external_link_list_url": reverse("tinymce-linklist")},
                 )
@@ -26,7 +26,7 @@ class TinyMCEFlatPageAdmin(FlatPageAdmin):
     def formfield_for_dbfield(self, db_field, **kwargs):
         if db_field.name == "content":
             return db_field.formfield(
-                widget=TinyMCE(
+                widget=AdminTinyMCE(
                     attrs={"cols": 80, "rows": 30},
                     mce_attrs={"external_link_list_url": reverse("tinymce-linklist")},
                 )
@@ -40,7 +40,7 @@ class TinyMCETestPageAdmin(admin.ModelAdmin):
     def formfield_for_dbfield(self, db_field, **kwargs):
         if db_field.name in ("content1", "content2"):
             return db_field.formfield(
-                widget=TinyMCE(
+                widget=AdminTinyMCE(
                     attrs={"cols": 80, "rows": 30},
                     mce_attrs={"external_link_list_url": reverse("tinymce-linklist")},
                 )
@@ -51,3 +51,4 @@ def formfield_for_dbfield(self, db_field, **kwargs):
 admin.site.unregister(FlatPage)
 admin.site.register(FlatPage, TinyMCEFlatPageAdmin)
 admin.site.register(TestPage, TinyMCETestPageAdmin)
+admin.site.register(TestModel)