Add ClubMembership enhancements, CSV import command, and related tests

- Extend the ClubMembership model with `club`, `member`, and optional `license` fields, along with relevant constraints and ordering.
- Implement verbose names for Club and ClubMembership models and update admin configurations for better display and filtering.
- Add a `import_members_csv` management command for batch importing members, clubs, and memberships from a CSV file.
- Include extensive tests for the `import_members_csv` command, ClubMembership model, and Club model.
- Refactor related migrations, services, and test structure.

authentication/management/commands/import_members_csv.py

@@ -0,0 +1,43 @@
+from django.core.management.base import BaseCommand, CommandError
+
+from authentication.services.member_csv_importer import MemberCsvImporter
+
+
+class Command(BaseCommand):
+    help = "Import club members from a CSV file."
+
+    def add_arguments(self, parser) -> None:
+        parser.add_argument(
+            "csv_file",
+            type=str,
+            help="Path to the CSV file to import.",
+        )
+        parser.add_argument(
+            "--date-format",
+            default="%Y-%m-%d",
+            help="Date format for date_of_birth. Default: %%Y-%%m-%%d",
+        )
+
+    def handle(self, *args, **options) -> str | None:
+        importer = MemberCsvImporter(date_format=options["date_format"])
+
+        try:
+            result = importer.import_path(options["csv_file"])
+        except Exception as exc:
+            raise CommandError(str(exc)) from exc
+
+        for error in result.errors:
+            self.stderr.write(self.style.ERROR(f"Row {error.row_number} skipped: {error.message}"))
+
+        self.stdout.write(
+            self.style.SUCCESS(
+                "Import complete. "
+                f"Members created: {result.created_members}. "
+                f"Members updated: {result.updated_members}. "
+                f"Users created: {result.created_users}. "
+                f"Clubs created: {result.created_clubs}. "
+                f"Memberships created: {result.created_memberships}. "
+                f"Memberships updated: {result.updated_memberships}. "
+                f"Rows skipped: {result.skipped_rows}."
+            )
+        )