在这种情况下，我将为用户创建一个序列化程序，然后在FriendshipRequestSerializer中使用它。

class UserSerializer(serializers.ModelSerializer):
    
    class Meta:
        model = User
        fields = ('id', 'first_name', 'last_name',)

class FriendshipRequestSerialiser(serializers.ModelSerializer):
    to_user = UserSerializer(many=False)
    from_user = UserSerializer(many=False)

    class Meta:
        model = FriendshipRequest
        fields = ('id', 'to_user', 'from_user', 'message', ...
        extra_kwargs = ...