What would be the equivalent of " $push: ‘$$ROOT’ " command in an aggregate query, when using the Mongo Csharp driver ? What would be the c# equivalent of the following json query (containing $push: ‘$$ROOT’) when using the mongodb csharp driver, with the fluent aggregate or linq (eventually using the new Linq3 provider) syntax:
db.getCollection('customers').aggregate(
[
  { $match:
     { $and:
     [
      { RegistrationDate: { $lte: ISODate('2021-12-13T23:59:59.999Z'), $gte: ISODate('2011-11-22T00:00:00.0Z') }},
      { $or:
        [
          { CountryOfResidence: 'France'},
          { CountryOfResidence: 'Spain'}
        ]
      },
      { Age: {$gte: '40'}}
     ]
     }
   },
   { $group: { _id: '$LastName', count: { $sum: 1 }, data: { $push: '$$ROOT' } } },
   { $match: { count: { $gte: 2 } } }, { $project: { count: 0 } }
])