[Enhancement] Refactor of license django model (#187)

Fixes #119

Licenses are now created in the bootstrap management command. To only create the licenses use the command line argument `-ol` or `--only-licenses`.
These licenses are then fetched by there `cc_string` when adding a license to a package.

Co-authored-by: Liam Brydon <62733830+MyCreativityOutlet@users.noreply.github.com>
Co-authored-by: jebus <lorsbach@envipath.com>
Co-authored-by: Tim Lorsbach <tim@lorsba.ch>
Reviewed-on: enviPath/enviPy#187
Co-authored-by: liambrydon <lbry121@aucklanduni.ac.nz>
Co-committed-by: liambrydon <lbry121@aucklanduni.ac.nz>

epdb/migrations/0010_license_cc_string.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.2.7 on 2025-11-11 14:11
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("epdb", "0009_joblog"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="license",
+            name="cc_string",
+            field=models.TextField(default="by-nc-sa", verbose_name="CC string"),
+            preserve_default=False,
+        ),
+    ]