Footnote make Page and UUID unique together (#16)

* Make Footnotes unique on page-uuid

* Add migration

* Fix migration and Footnote.DoesNotExist exception

* Footnote.DoesNotExist is no longer needed

We no longer run .get(), instead we store a list of the page's footnotes, we will get a KeyError if there is an invalid footnote reference.

Author: Cameron Lamb

CHANGELOG.md

@@ -5,6 +5,7 @@
 - Clean up old step from README - It is no longer recommended to define footnotes in `WAGTAILADMIN_RICH_TEXT_EDITORS`
 - Add `footnotes` rich text feature automatically
 - Clean up `RichTextBlockWithFootnotes`
+- Make Footnotes unique on `page` <-> `uuid`
 
 ## 0.6.0
 

wagtail_footnotes/migrations/0002_alter_footnote_unique_together.py

@@ -0,0 +1,27 @@
+# Generated by Django 3.2.4 on 2021-06-24 10:18
+
+from django.db import migrations
+import wagtail_footnotes.fields
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("wagtailcore", "0041_group_collection_permissions_verbose_name_plural"),
+        ("wagtail_footnotes", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.AlterUniqueTogether(
+            name="footnote",
+            unique_together={("page", "uuid")},
+        ),
+        migrations.AlterField(
+            model_name="footnote",
+            name="uuid",
+            field=wagtail_footnotes.fields.CustomUUIDField(
+                help_text="The ID of the footnote is shown in the rich text editor for reference.",
+                verbose_name="ID",
+            ),
+        ),
+    ]

wagtail_footnotes/models.py

@@ -17,17 +17,17 @@ class Footnote(models.Model):
 
     page = ParentalKey("wagtailcore.Page", related_name="footnotes")
     uuid = CustomUUIDField(
-        unique=True,
         verbose_name="ID",
         help_text="The ID of the footnote is shown in the rich text editor for "
         "reference.",
     )
     text = RichTextField(
         features=getattr(
-            settings, 
-            'WAGTAIL_FOOTNOTES_TEXT_FEATURES', 
-            ["bold", "italic", "link"]
+            settings, "WAGTAIL_FOOTNOTES_TEXT_FEATURES", ["bold", "italic", "link"]
         )
     )
 
     panels = [FieldPanel("text"), FieldPanel("uuid", widget=ReadonlyUUIDInput)]
+
+    class Meta:
+        unique_together = ("page", "uuid")