feat: Add event co-managers permissions and allow managers/admins to signup guests on skill-restricted shifts

backend/apps/events/serializers.py

@@ -1,5 +1,9 @@
 from rest_framework import serializers
+from django.contrib.auth import get_user_model
 from .models import Skill, Event, TaskArea, Shift, ShiftSignup, EventTemplate
+from apps.users.serializers import UserSerializer
+
+User = get_user_model()
 
 class SkillSerializer(serializers.ModelSerializer):
     class Meta:
@@ -65,12 +69,17 @@ class TaskAreaSerializer(serializers.ModelSerializer):
 class EventSerializer(serializers.ModelSerializer):
     task_areas = TaskAreaSerializer(many=True, read_only=True)
     created_by_name = serializers.SerializerMethodField()
+    co_managers = UserSerializer(many=True, read_only=True)
+    co_manager_ids = serializers.PrimaryKeyRelatedField(
+        queryset=User.objects.all(), many=True, write_only=True, required=False, source='co_managers'
+    )
 
     class Meta:
         model = Event
         fields = [
             'id', 'title', 'description', 'location',
             'start_date', 'end_date', 'is_active', 'created_by', 'created_by_name',
+            'co_managers', 'co_manager_ids',
             'task_areas', 'created_at', 'updated_at'
         ]
         read_only_fields = ['created_by', 'created_at', 'updated_at']