* adds store package for wrapping model_store
Introduces the pkg/store package, which contains funcs
for wrapping the model_store with common requests.
This package choice was made for its combination
of being in an accessible place, centralizing functionality
and not introducing circular dependencies.
* Split KopiaWrapper into repo handle and logic
With ModelStore, multiple structs need a reference to the kopia repo.
Make a small wrapper class (conn) that can open and initialize a repo. The
wrapper handles concurrent closes and opens and does ref counting to
ensure it only drops the kopia handle when the last reference is closed.
Rename KopiaWrapper to Wrapper and keep backup/restore functionality
in it.
* Implement ModelStore GetByType and Get
* Add tests for ModelStore Get functions
* Add stricter "type" checks for loaded models
Take modelType as parameter and check the model in question matches that
type. Adds a little extra layer of protection if models happen to have
the same struct layout.
* Add ModelStore Update operation
* Tests for ModelStore Update function
* Add regression test for error during Update()
Ensure that if an error occurs during a ModelStore update operation the
previously stored model remains unchanged and no new model is visible to
the user.
* Simple Get and Put implementations
Get implementation is currently the one that uses the kopia ID of the
model/manifest.
* Basic tests for ModelStore Get/Put
