Making fieldDefinitions optional in metaobjectDefinitionCreate

Starting in April 2026, the fieldDefinitions input argument for the metaobjectDefinitionCreate mutation will become optional. This change means that developers will no longer be required to specify fieldDefinitions when creating a new metaobject definition. Existing implementations that rely on fieldDefinitions will continue to function as before, but developers can now choose to omit this argument if it is not needed for their specific use case.