ProjectSerializer.py

class ProjectSerializer(DetailSerializer, ModelSerializer):
    users = UserSerializer(many=True, read_only=True)
    organization = OrganizationSerializer(read_only=True)
    
    class Meta:
        model = Project
        fields = ('id', 'organization', 'country', 'name', 'description', 
                  'archived', 'urls', 'contacts', 'users')
        read_only_fields = ('id', 'country',)
        detail_only_fields = ('users',)
        
    def create(self, validated_data):
        organization = self.context['organization']
        return Project.objects.create(
            organization_id=organization.id,
            **validated_data
        )