✨(backend) allow users to mark/unmark documents as favorite

A user can now mark/unmark documents as favorite.
This is done via a new action of the document API endpoint:
/api/v1.0/documents/{document_id}/favorite
POST to mark as favorite / DELETE to unmark

src/backend/core/migrations/0009_add_document_favorite.py

@@ -0,0 +1,37 @@
+# Generated by Django 5.1.2 on 2024-11-08 07:59
+
+import django.db.models.deletion
+import uuid
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('core', '0008_alter_document_link_reach'),
+    ]
+
+    operations = [
+        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'),
+        ),
+        migrations.CreateModel(
+            name='DocumentFavorite',
+            fields=[
+                ('id', models.UUIDField(default=uuid.uuid4, editable=False, help_text='primary key for the record as UUID', primary_key=True, serialize=False, verbose_name='id')),
+                ('created_at', models.DateTimeField(auto_now_add=True, help_text='date and time at which a record was created', verbose_name='created on')),
+                ('updated_at', models.DateTimeField(auto_now=True, help_text='date and time at which a record was last updated', verbose_name='updated on')),
+                ('document', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='favorited_by_users', to='core.document')),
+                ('user', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='favorite_documents', to=settings.AUTH_USER_MODEL)),
+            ],
+            options={
+                'verbose_name': 'Document favorite',
+                'verbose_name_plural': 'Document favorites',
+                'db_table': 'impress_document_favorite',
+                'constraints': [models.UniqueConstraint(fields=('user', 'document'), name='unique_document_favorite_user', violation_error_message='This document is already targeted by a favorite relation instance for the same user.')],
+            },
+        ),
+    ]