Couldn't update subscription with default values

[dnikolay-ebc]

Describe the bug
Method update_subscription of filip.clients.ngsi_v2.ContextBrokerClient has following configuration for request serialization:

res = self.patch(
                url=url,
                headers=headers,
                data=subscription.json(exclude={'id'},
                                       exclude_unset=True,
                                       exclude_defaults=True,
                                       exclude_none=True))

If a subscription is created/updated with non default values you can never re-set the default ones because defaults are excluded from serialization.

To Reproduce
Steps to reproduce the behavior:

As an example try to update the status of a subscription:

        with ContextBrokerClient(url='http://localhost:1026',
                                 fiware_header=FiwareHeader(
                                     service='fw-service',
                                     service_path='/testing',
                                 )) \
                as cb_client:

            subscription = cb_client.get_subscription('xyz')
            subscription.status = Status.INACTIVE

            cb_client.update_subscription(subscription)

→ subscription updates status to "inactive"

            subscription.status = Status.ACTIVE
            cb_client.update_subscription(subscription)

→ subscription still has status "inactive"

Environment (please complete the following information):

• OS: Windows 10
• Version 20H2
• Python 3.8

[dnikolay-ebc]

update_registration has same issue.

[tstorek]

@dnikolay-ebc which version of the library are you currently using?

[tstorek]

@dnikolay-ebc

I tested with a small example:

from pydantic import BaseModel, Field

class Model(BaseModel):
    test: str = Field(default='123')

model = Model(test='123')
print(model.json(exclude_defaults=True))

Does indeed skip the default although set, while

print(model.json(exclude_defaults=False))

would do the trick.
I am actually surprised by this behavior of pydantic.

We will correct this as soon as possible. However, this has to wait until #24 will be merged because this will probably come along with a breaking change