Content-addressable backend store.
Content-addressable stores are store where it is possible to read and add new values. Keys are derived from the values raw contents and hence are deterministic.
The type for content-addressable backend stores. The
'a phantom type carries information about the store mutability.
find t k is
Some v if
k is associated to
k is not present in
Write the contents of a value to the store. It's the responsibility of the content-addressable store to generate a consistent key.
add but allows to specify the key directly. The backend might choose to discared that key and/or can be corrupt if the key scheme is not consistent.