Error in backend calling fetch more than once when archive is set

[sduenas]

When we implemented the Archive object, we considered it will only store the items of a single fetch call. It can't be reused to store the raw responses of several fetch tasks.

If the archive is set, it will produce an error because the archive object is given when the object is initialized and not when fetch is called.

To fix this issue, #527 must be completed first.