Adds SQL steps to move author data to the new table

bookwyrm/migrations/0155_book_new_authors.py

@@ -0,0 +1,44 @@
+# Generated by Django 3.2.14 on 2022-07-09 21:21
+
+import bookwyrm.models.fields
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("bookwyrm", "0154_bookauthor"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="book",
+            name="new_authors",
+            field=bookwyrm.models.fields.ManyToManyField(
+                related_name="new_authors",
+                through="bookwyrm.BookAuthor",
+                to="bookwyrm.Author",
+            ),
+        ),
+        migrations.RunSQL(
+            sql="""
+INSERT INTO bookwyrm_bookauthor (id, book_id, author_id, created_date, updated_date, author_type)
+SELECT id, book_id, author_id, NOW(), NOW(), 'author' from bookwyrm_book_authors;
+            """,
+            reverse_sql="""
+INSERT INTO bookwyrm_book_authors (id, book_id, author_id)
+SELECT id, book_id, author_id from bookwyrm_bookauthor;
+            """,
+        ),
+        migrations.RemoveField(model_name="book", name="authors"),
+        migrations.RenameField(
+            model_name="book", old_name="new_authors", new_name="authors"
+        ),
+        migrations.AlterField(
+            model_name="book",
+            name="authors",
+            field=bookwyrm.models.fields.ManyToManyField(
+                through="bookwyrm.BookAuthor", to="bookwyrm.Author"
+            ),
+        ),
+    ]

bookwyrm/models/book.py

@@ -114,10 +114,9 @@ class Book(BookDataModel):
     subject_places = fields.ArrayField(
         models.CharField(max_length=255), blank=True, null=True, default=list
     )
-    authors = fields.ManyToManyField("Author")
-    # authors = fields.ManyToManyField(
-    #    "Author", through="BookAuthor", through_fields=("book", "author")
-    # )
+    authors = fields.ManyToManyField(
+        "Author", through="BookAuthor", through_fields=("book", "author")
+    )
     cover = fields.ImageField(
         upload_to="covers/", blank=True, null=True, alt_field="alt_text"
     )