new MongoDbRepository<Registration>()
	.Query(user => user.Any(x => x.Email == userRegistration.Email))  //returns bool

new MongoDbRepository<Authentication>()
	.Query(auth => auth
		.Where(x => x.Email == Email)
		.Where(x => x.Password == Password)
		.FirstOrDefault()); // Returns single Authentication or null

new MongoDbRepository<Character>()
	.Query(c => c.Select(x => x.Name).ToList()); // Returns list of character names