Customer price model is created despite of incomplete request body

[adamczykba]

Describe the bug
When defining the customer price model for the first time, it is updated despite of the error being thrown due to incomplete PUT request body.

To Reproduce
Steps to reproduce the behavior:

1. Send PUT request to /services/[service_id]/pricemodel/customer/[customer_id] without all required parameters in the request body
2. Observe error message in the response
3. Check the price model for the service for given customer

Expected behavior
Price model for customer was not updated

Observed behavior
Price model for customer is created despite of error (its values are copied from previously defined pricemodel for the service)

Screenshots

Additional context
N/A