Update member UI and related app changes

src/ccma/ui/dialogs.py

@@ -19,7 +19,7 @@ class NewMemberDialog(tk.Toplevel):
         self.number_policy = repository.get_member_number_policy()
         self.variables = {
             name: tk.StringVar()
-            for name in ("first_name", "last_name", "email", "phone", "birth_date", "member_number")
+            for name in ("first_name", "last_name", "nickname", "email", "phone", "birth_date", "member_number")
         }
         self._build_ui()
         self.bind("<Escape>", lambda _event: self.destroy())
@@ -32,6 +32,7 @@ class NewMemberDialog(tk.Toplevel):
         fields = [
             ("Vorname *", "first_name"),
             ("Nachname *", "last_name"),
+            ("Nickname", "nickname"),
             ("E-Mail-Adresse", "email"),
             ("Telefonnummer", "phone"),
             (f"Geburtsdatum ({date_input_hint()})", "birth_date"),