@callback delete_membership(context(), group_id(), pubkey()) :: :ok | {:error, reason()}

@callback delete_role(context(), group_id(), pubkey(), binary()) ::
  :ok | {:error, reason()}

@callback get_membership(context(), group_id(), pubkey()) ::
  {:ok, membership() | nil} | {:error, reason()}

@callback list_memberships(context(), group_id()) ::
  {:ok, [membership()]} | {:error, reason()}

@callback list_roles(context(), group_id(), pubkey()) ::
  {:ok, [role()]} | {:error, reason()}

@callback put_membership(context(), membership()) ::
  {:ok, membership()} | {:error, reason()}

@callback put_role(context(), role()) :: {:ok, role()} | {:error, reason()}