Remove Ponos from CE

Based on !2227 (merged)

TODO:

• Remove & update tests

arkindex/ponos/migrations/0001_initial.py

@@ -9,7 +9,6 @@ import enumfields.fields
 from django.contrib.postgres.operations import HStoreExtension
 from django.db import migrations, models
 
-import arkindex.ponos.keys
 import arkindex.ponos.models
 import arkindex.project.fields
 import arkindex.project.validators
@@ -77,7 +76,7 @@ class Migration(migrations.Migration):
             fields=[
                 ("id", models.UUIDField(default=uuid.uuid4, primary_key=True, serialize=False)),
                 ("name", models.CharField(max_length=250, unique=True)),
-                ("nonce", models.BinaryField(default=arkindex.ponos.keys.gen_nonce, max_length=16)),
+                ("nonce", models.BinaryField(default=arkindex.ponos.models.gen_nonce, max_length=16)),
                 ("content", models.BinaryField(editable=True)),
             ],
         ),