Support MSC3391: Account data deletion (#2967)

* add deleteAccountData endpoint

* check server support and test

* test current state of memorystore

* interpret account data events with empty content as deleted

* add handling for (future) stable version of endpoint

* add getSafeUserId

* user getSafeUserId in deleteAccountData

* better jsdoc for throws documentation

spec/unit/stores/memory.spec.ts

@@ -0,0 +1,65 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { MatrixEvent, MemoryStore } from "../../../src";
+
+describe("MemoryStore", () => {
+    const event1 = new MatrixEvent({ type: "event1-type", content: { test: 1 } });
+    const event2 = new MatrixEvent({ type: "event2-type", content: { test: 1 } });
+    const event3 = new MatrixEvent({ type: "event3-type", content: { test: 1 } });
+    const event4 = new MatrixEvent({ type: "event4-type", content: { test: 1 } });
+    const event4Updated = new MatrixEvent({ type: "event4-type", content: { test: 2 } });
+    const event1Empty = new MatrixEvent({ type: "event1-type", content: {} });
+
+    describe("account data", () => {
+        it("sets account data events correctly", () => {
+            const store = new MemoryStore();
+            store.storeAccountDataEvents([event1, event2]);
+            expect(store.getAccountData(event1.getType())).toEqual(event1);
+            expect(store.getAccountData(event2.getType())).toEqual(event2);
+        });
+
+        it("returns undefined when no account data event exists for type", () => {
+            const store = new MemoryStore();
+            expect(store.getAccountData("my-event-type")).toEqual(undefined);
+        });
+
+        it("updates account data events correctly", () => {
+            const store = new MemoryStore();
+            // init store with event1, event2
+            store.storeAccountDataEvents([event1, event2, event4]);
+            // remove event1, add event3
+            store.storeAccountDataEvents([event1Empty, event3, event4Updated]);
+            // removed
+            expect(store.getAccountData(event1.getType())).toEqual(undefined);
+            // not removed
+            expect(store.getAccountData(event2.getType())).toEqual(event2);
+            // added
+            expect(store.getAccountData(event3.getType())).toEqual(event3);
+            // updated
+            expect(store.getAccountData(event4.getType())).toEqual(event4Updated);
+        });
+
+        it("removes all account data from state on deleteAllData", async () => {
+            const store = new MemoryStore();
+            store.storeAccountDataEvents([event1, event2]);
+            await store.deleteAllData();
+
+            // empty object
+            expect(store.accountData).toEqual({});
+        });
+    });
+});