Separate fetch/save api into plugin or external module

It would be great if in the second version of the library the model and collection got rid of the built-in backend API.
In my opinion, the backend API should be an external module, although it is possible to provide a base implementation.
Today, you constantly have to look for workarounds if you want to destroy a model that does not imply synchronization, but has the specified Id.
And in general, if we are talking about the model-view concept, in my opinion it would be better if the library will be not aware of the backend
Besides, this separation will simplify the process of getting rid of jQuery if such an idea arises.

Start by reviewing how the model and collection currently use the built-in backend API, especially the destroy case for models with an id but no synchronization. The issue proposes an external module or plugin with a possible base implementation and reduced jQuery coupling; completion would require a settled design for that separation.

Written by the indexing model from the issue text.