Represent tracing media as symbols and add pool thumbnails

clips/migrations/0015_tracing_images.py

@@ -0,0 +1,48 @@
+"""Schema 6: tracing is a symbol.
+
+A face's `:head :trace` is gone: its footage is a placement of a `:type :trace`
+symbol under the head, the trace keys are that placement's `:time :holds`, and the
+head follows them with `:reads`. Nothing is converted. Every project is marked 6,
+and one that still carries a `:trace` is refused when it is opened, by name and
+with what to do about it; the rest open as they did.
+
+Images are stills to trace over, stored like sounds.
+"""
+
+import uuid
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+def forwards(apps, schema_editor):
+    apps.get_model("clips", "Project").objects.update(schema_version=6)
+
+
+class Migration(migrations.Migration):
+    dependencies = [("clips", "0014_multiple_analyses")]
+
+    operations = [
+        migrations.CreateModel(
+            name="Image",
+            fields=[
+                ("id", models.UUIDField(default=uuid.uuid4, editable=False,
+                                        primary_key=True, serialize=False)),
+                ("filename", models.CharField(max_length=255)),
+                ("label", models.CharField(
+                    blank=True, max_length=200,
+                    help_text="what a person called it; the filename when empty")),
+                ("width", models.PositiveIntegerField(help_text="pixels, as ffprobe reports them")),
+                ("height", models.PositiveIntegerField()),
+                ("created", models.DateTimeField(auto_now_add=True)),
+                ("blob", models.ForeignKey(on_delete=django.db.models.deletion.PROTECT,
+                                           related_name="image_for", to="clips.blob")),
+            ],
+        ),
+        migrations.AlterField(
+            model_name="project",
+            name="schema_version",
+            field=models.PositiveIntegerField(default=6),
+        ),
+        migrations.RunPython(forwards, migrations.RunPython.noop),
+    ]