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.

club/admin.py

@@ -1,3 +1,24 @@
 from django.contrib import admin
+from django.utils.translation import gettext_lazy as _
+
+from .models import Club, ClubMembership
+
 
 # Register your models here.
+@admin.register(Club)
+class ClubAdmin(admin.ModelAdmin):
+    list_display = ["name"]
+    search_fields = ["name"]
+    ordering = ["name"]
+
+
+@admin.register(ClubMembership)
+class ClubMembershipAdmin(admin.ModelAdmin):
+    list_display = ["club__name", "member__last_name", "member__first_name", "license"]
+    search_fields = ["club__name", "member__last_name", "member__first_name"]
+    list_filter = ["club"]
+    raw_id_fields = ["member"]
+    fieldsets = [
+        [None, {"fields": ["club", "member"]}],
+        [_("Member informaton"), {"fields": ["license"]}],
+    ]