Update Foreign-key Related Instance on Post Request - django-rest-framework

Question

I am trying to implement a system where a user can subscribe to a company. For that I have to implement the following flow:
User registers
User klicks on a button to subscribe to a company
User has to enter a code (every company has a secret code. By possession the user proves that he is somewhat related to the company)
User is subscribed
For this, I have to implement an API endpoint that receives the code by the user (the user is authenticated at this point).
It is shameful, but I am lost: I am thinking of implementing a view like this.
class RegisterUserToCustomer(APIView):
permission_classes = (permissions.IsAuthenticated,)
def post(self, request, format=None):
serializer = CustomerSerializer(data=request.data)
if serializer.is_valid():
serializer.save(user=self.request.user)
return Response(serializer.data, status=status.HTTP_201_CREATED)
return Response(serializer.data, status=status.HTTP_400_BAD_REQUEST)
Obviously, I have to:
Receive the code from the user via POST method
Search the database and figure out, if the code corresponds to any company
Edit the ForeignKey field on the user and link it to the company
But where would I implement this logic. With my limited experience I see three possibilities:
Call serializer.save() and write a custom create() method (but I don't want to create anything so this seems like bad practice
Implement this logic in the view, but I want to access the code from the validated_data (this seems like a problem?)
Can I write a custom save() method for the serializer? Are there any examples for a custom save() method since the original drf save() method contains a lot of validation logic.
Obviously I don't expect you guys to write the whole code for me, but maybe someone has somewhat of a blueprint of how and where to implement this?

Answer 1

Steps to do this:
Create a field company_code in Customer table and make that
field as Foreign key.
Create a Serializer with that foreign key field.
Create a viewset or generic views to expect that field from Post method as Id of the Company. Use save() method to store foreign key.
This scenarios is only for Subscribe one organisation, if you're able to subscribe multiple organisation make that field as ManytoMany field.
Refer the code sample,
Models.py
class Customer(models.Model):
# customer related field
name = models.CharField(max_length=20)
organization = models.ForeignKey(Organization, on_delete=models.CASCADE)
Serializer.py
class CustomerSerializer(serializers.ModelSerializer):
class Meta:
model = User
fields = ('name', 'organization', )
Views.py
class CustomerViewSet(viewsets.ModelViewSet):
serializer_class = CustomerSerializer
queryset = Customer.objects.all()
Request data(POST Json)
{
"name": "test",
"organization": "id-of company"
}