[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/0011_auto_20251111_1413.py

@@ -0,0 +1,59 @@
+# Generated by Django 5.2.7 on 2025-11-11 14:13
+
+import re
+
+from django.contrib.postgres.aggregates import ArrayAgg
+from django.db import migrations
+from django.db.models import Min
+
+
+def set_cc(apps, schema_editor):
+    License = apps.get_model("epdb", "License")
+
+    # For all existing licenses extract cc_string from link
+    for license in License.objects.all():
+        pattern = r"/licenses/([^/]+)/4\.0"
+        match = re.search(pattern, license.link)
+        if match:
+            license.cc_string = match.group(1)
+            license.save()
+        else:
+            raise ValueError(f"Could not find license for {license.link}")
+
+    # Ensure we have all licenses
+    cc_strings = ["by", "by-nc", "by-nc-nd", "by-nc-sa", "by-nd", "by-sa"]
+    for cc_string in cc_strings:
+        if not License.objects.filter(cc_string=cc_string).exists():
+            new_license = License()
+            new_license.cc_string = cc_string
+            new_license.link = f"https://creativecommons.org/licenses/{cc_string}/4.0/"
+            new_license.image_link = f"https://licensebuttons.net/l/{cc_string}/4.0/88x31.png"
+            new_license.save()
+
+    # As we might have existing Licenses representing the same License,
+    # get min pk and all pks as a list
+    license_lookup_qs = License.objects.values("cc_string").annotate(
+        lowest_pk=Min("id"), all_pks=ArrayAgg("id", order_by=("id",))
+    )
+
+    license_lookup = {
+        row["cc_string"]: (row["lowest_pk"], row["all_pks"]) for row in license_lookup_qs
+    }
+
+    Packages = apps.get_model("epdb", "Package")
+
+    for k, v in license_lookup.items():
+        # Set min pk to all packages pointing to any of the duplicates
+        Packages.objects.filter(pk__in=v[1]).update(license_id=v[0])
+        # remove the min pk from "other" pks as we use them for deletion
+        v[1].remove(v[0])
+        # Delete redundant License objects
+        License.objects.filter(pk__in=v[1]).delete()
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("epdb", "0010_license_cc_string"),
+    ]
+
+    operations = [migrations.RunPython(set_cc)]