Add validation logic for the extra column of container_registries

[jopemachine]

Follow-up to #2621, #2622, #2623, #2624.

Main idea

container_registries.extra column allows different values depending on the registry type.
Let’s add validation logic for the extra column to the container registry API.

Schema

Github container registries

• entity_type: str (users or groups)

Gitlab container registries

• api_endpoint: str

AWS ECR

• access_token: str
• secret_access_token: str
• region: str (e.g. us-east-1)