Enhance adventure management: add error handling for category fetch, implement unique email constraint in user model, and update adventure save logic to ensure category assignment

backend/server/users/models.py

@@ -4,6 +4,7 @@ from django.db import models
 from django_resized import ResizedImageField
 
 class CustomUser(AbstractUser):
+    email = models.EmailField(unique=True)  # Override the email field with unique constraint
     profile_pic = ResizedImageField(force_format="WEBP", quality=75, null=True, blank=True, upload_to='profile-pics/')
     uuid = models.UUIDField(default=uuid.uuid4, editable=False, unique=True)
     public_profile = models.BooleanField(default=False)