ImageAsset
data class ImageAsset(val tag: String, val width: Int, val height: Int, val originalWidth: Int, val originalHeight: Int, val mimeType: String, val size: Int, val otrKey: ByteArr? = null, val macKey: ByteArr? = null, val mac: ByteArr? = null, val sha256: ByteArr? = null, val unknownFields: Map<Int, UnknownField> = emptyMap()) : Message