Appending to referenced enum #2941

Would love to be able to append to an existing enum. Not all values are applickable in all cases, this means that i need to redefine the enum. Especially when used together with deepmap's oapi-gen this would be nice.

Example:
SensorType.yaml:
type: string
enum: [Motion, Push, Voice]

Doorbell.yaml:
schema:
$ref: "#/shared/components/schemas/SensorType.yaml"
description: Sensor to trigger doorbell

Alarm.yaml:
schema:
$ref: "#/shared/components/schemas/SensorType.yaml"
append: [ Temp, Vibration, SignalLoss ]
description: Sensor to trigger alarm