Override conversion for STL-like user types

[Numendacil]

Suppose i have the following struct foo, which defines a begin and end function for the convenience of ranged-for loops

struct foo
{
    std::string tag;
    std::vector<int> data;
    ...
    iterator begin() { return this->data.begin(); }
    iterator end() { return this->data.end(); }
    // so i can use for (const auto& p : foo), etc
};

Now if i try to define a custom conversion to json by

void from_json(const json& j, foo& p)
{
    p.tag = j.at("tag").get<std::string>();
    p.data = j.at("data").get<std::vector<int>>();
    ...
}

It would not work, since the existence of iterator functions would made the library use the default serialization as if std::vector<int> is present, i.e. get<foo>() is like get<std::vector<int>>() with the results stored in foo::data.
Therefore my question is that is there a way to override this default behaviour or i have to choose between ranged-for and custom conversions?

[falbrechtskirchinger]

A related issue is very high on my to-do list. I'll take your use case into account when I get to it.

You can probably work around the issue by implementing a custom serializer that forwards to the default serializer for all types but foo.