Data Product Creation Fails When Domain is Not Specified Due to Pydantic Treating it as None

[Prajwal214]

Affected module
Does it impact the UI, backend or Ingestion Framework?
-- Backend

Describe the bug
A clear and concise description of what the bug is.
-- While creating Data Product using SDK, when domain field is not specified it is getting created as Pydantic is considering the domain as None. Domain should be required for Data Product to be created.

{
  "responseMessage" : "An exception with message [Cannot invoke \"org.openmetadata.schema.type.EntityReference.getId()\" because the return value of \"org.openmetadata.schema.entity.domains.DataProduct.getDomain()\" is null] was thrown while processing request.",
  "errorType" : "UNHANDLED_SERVER_EXCEPTION"
}

We would also need a example for creating Data Product in the example_apis.py

To Reproduce

Screenshots or steps to reproduce

Expected behavior
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Version:

• OS: [e.g. iOS]
• Python version:
• OpenMetadata version: [e.g. 0.8]
• OpenMetadata Ingestion package version: [e.g. openmetadata-ingestion[docker]==XYZ]

Additional context
Add any other context about the problem here.