Pass a store implementation rather than kind string.
Pass a store implementation rather than kind string.

Makes it easier to test.

krombel/matrix-js-sdk,williamboman/matrix-js-sdk,matrix-org/matrix-js-sdk,matrix-org/matrix-js-sdk,williamboman/matrix-js-sdk,matrix-org/matrix-js-sdk,krombel/matrix-js-sdk,matrix-org/matrix-js-sdk,krombel/matrix-js-sdk,williamboman/matrix-js-sdk