title: ManytoMany relationship serializer
body: <p>I've encountered a huge problem with a single Many to many relationship, Im trying to send the id's of the users to the group serializer in order for me to save them and create the group however the id is never recorded and grupos is created with nothing but saves nombre and creates the object.</p>
  
  <p>Models.py</p>
  
  <pre><code>class Usuarios(models.Model):
  class Meta:
      db_table = "Usuarios"
  idUsuario = models.AutoField(primary_key=True)
  tipoUsuario = models.BooleanField(blank=False)
  nombre = models.CharField(max_length=100,blank=False)
  idUser = models.IntegerField(blank=False)
  idEscuela = models.ForeignKey(Escuelas, on_delete=models.CASCADE)
  
  class Grupos(models.Model):
  class Meta:
      db_table = "Grupos"
  idGrupo = models.AutoField(primary_key=True)
  nombre = models.CharField(max_length=30,blank=False,unique=True)
  idUsuario = models.ManyToManyField(Usuarios)
  
  class idUsuarioSerializer(serializers.Serializer):
  #idUsuario = serializers.IntegerField(required=True)
  class Meta:
      model = Usuarios
      fields = ('idUsuario',)
  
  
  class GrupoSerializer(serializers.Serializer):
      nombre = serializers.CharField(required=True)
      idUsuario = idUsuarioSerializer(many=True)
      class Meta:
          model = Grupos
          fields = ('nombre','idUsuario')
      def create(self, validated_data):
  
          idUsuarios_data = validated_data.pop('idUsuario')
          grupo = Grupos.objects.create(**validated_data)
          for idUsuario_data in idUsuarios_data:
              #print(**idUsuario_data)
              #Usuarios.objects.create(grupo=grupo,**idUsuario_data)
              grupo.idUsuario.add(**idUsuario_data)
          grupo.save()
          return grupo
  </code></pre>
  
  <p>However this saves nothing on idUsuario field and also if I do it like the documentation it gives me an error "group is not a valid keyword" or even if I use "idGrupo" it says the same, I already check other answers looks like it's not possible, already tried add method too.</p>
  
  <p>I send the following json</p>
  
  <pre><code>{
  "nombre": "4B",
  "idUsuario":[{"id":1},{"id":2}]
   }
  </code></pre>