GODRIVER-1919 Add object id decoder awareness of string hex

[glossd]

Try to run this code

type Entity struct {
	ID primitive.ObjectID `bson:"_id"`
}

func main() {
	var e Entity
	err := bson.UnmarshalExtJSON([]byte(`{"_id":"5ef7fdd91c19e3222b41b839"}`), true, &e)
	if err != nil {
		log.Fatal(err)
	}
}

You'll get an ObjectID string must be exactly 12 bytes long. Obvious bug

[benjirewis]

Thanks so much for your contribution to the driver @gl-ot ! I've authorized the CI patch build, and it looks like everything passes. We'll merge this and/or request changes once other team members have reviewed.

[divjotarora]

Thanks for the contribution @gl-ot! Just one small comment from me, but otherwise the change looks good.

[divjotarora]

I authorized a new CI patch, but this looks great. Thanks again!