Allow null value in the "in" operator. This will help reducing code to query if a document has a specific ID or null.
Helpfull when you have documents connected to a organization and/or a project.
So you can filter
{ in: { path: "project", value: [null, ID] }}

Currently you have to filter this with a combination of filter, compound, should and equals with a minimumShouldMatch: 1.

{
  compound: {
    should: [
      {
        equals: {
          path: 'project',
          value: null,
        },
      },
      {
        equals: {
          path: 'project',
          value: req.project._id,
        },
      },
    ],
      minimumShouldMatch: 1,
  },
}