The current status of the CreativeGroup.
This state is readonly to the client after it gets into a SUBMITTED state.
When a new CreativeGroup is created, it will be created in "SUBMITTED" state by default
and it requires all the validations to pass.
However, the client can specify "DRAFT" as the state in the creation request
to request the CreativeGroup be saved as a draft without mandating all the required data.
But any user entered data still need to pass their own validation individually for them
to be accepted by the Moloco Ads backend.
The client can switch a "DRAFT" Creative to "SUBMITTED" by specifying "SUBMITTED"
as the state value in an update request later after all required data are entered,
and full validation will be invoked on this state switch.
After a CreativeGroup gets out of the DRAFT state, the state will be fully managed by the Moloco Ads backend
and the state value will become readonly to the client.
Any state value specified by the client in the future update requests will be ignored.
