Add a convenience method to check for ObjectIds

[chris-steele]

Feature description

An identifier can be in string form or an instance of ObjectId. We can test for a string, but it would be useful to test for an ObjectId also.

Can you work on this feature?

• I can contribute

[taylortom]

I think we should probably add this to the existing ObjectIdUtils (referenced from the MongoDBModule instance):

const mongodb = await this.app.waitForModule('mongodb')
mongodb.ObjectId.isObjectId(id)