✨(backend) add server-to-server API endpoint to create documents

We want trusted external applications to be able to create documents
via the API on behalf of any user. The user may or may not pre-exist
in our database and should be notified of the document creation by
email.

src/backend/core/migrations/0012_make_document_creator_and_invitation_issuer_optional.py

@@ -0,0 +1,30 @@
+# Generated by Django 5.1.2 on 2024-11-30 22:23
+
+import django.db.models.deletion
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('core', '0011_populate_creator_field_and_make_it_required'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='document',
+            name='creator',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.RESTRICT, related_name='documents_created', to=settings.AUTH_USER_MODEL),
+        ),
+        migrations.AlterField(
+            model_name='invitation',
+            name='issuer',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.CASCADE, related_name='invitations', to=settings.AUTH_USER_MODEL),
+        ),
+        migrations.AlterField(
+            model_name='user',
+            name='language',
+            field=models.CharField(choices="(('en-us', 'English'), ('fr-fr', 'French'), ('de-de', 'German'))", default='en-us', help_text='The language in which the user wants to see the interface.', max_length=10, verbose_name='language'),
+        ),
+    ]