manage_session.RdProvides a blockr.core::preserve_board() using a pins::board_local() as
storage backend. The blockr.core::blockr_option() session_mgmt_backend
can be set to swap out this default pin board for another.
manage_session(server = manage_session_server, ui = manage_session_ui)
manage_session_server(id, board, ...)
manage_session_ui(id, board)