Hi no it did not come with a harness or switch. I mainly use the bike in the winter to clean snow so it doesn't matter to me if the light is connected to the headlight. I just need the hot that goes to the headlight on the handlebars.Hi I recommend you not wire into the headlight circuit because you are likely to want to control it separately.
Did it come with a harness and switch?
If not I would buy a harness and switch do it would have its own relay.
If so I would power it from the accessory circuit