Move crypto/recoverykey.ts to crypto-api/recovery-key.ts (#4399)

* Move `crypto/recoverykey.ts` to `crypto-api/recovery-key.ts`

* Re-export `crypto-api/recovery-key` into `crypto/recoverykey`

* Add a bit of doc

* Deprecate `MatrixClient.isValidRecoveryKey` and `MatrixClient.keyBackupKeyFromRecoveryKey`

* Import `index.ts` directly

* Update `recovery-key.ts` doc

* Add tests for `decodeRecoveryKey`

* Move `recovery-key.spec.ts` file

spec/unit/crypto-api/recovery-key.spec.ts

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2024 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 { decodeRecoveryKey, encodeRecoveryKey } from "../../../src/crypto-api";
+
+describe("recovery key", () => {
+    describe("decodeRecoveryKey", () => {
+        it("should thrown an incorrect length error", () => {
+            const key = [0, 1];
+            const encodedKey = encodeRecoveryKey(key)!;
+
+            expect(() => decodeRecoveryKey(encodedKey)).toThrow("Incorrect length");
+        });
+
+        it("should thrown an incorrect parity", () => {
+            const key = Array.from({ length: 32 }, (_, i) => i);
+            let encodedKey = encodeRecoveryKey(key)!;
+            // Mutate the encoded key to have incorrect parity
+            encodedKey = encodedKey.replace("EsSz", "EsSZ");
+
+            expect(() => decodeRecoveryKey(encodedKey!)).toThrow("Incorrect parity");
+        });
+
+        it("should decode a valid encoded key", () => {
+            const key = Array.from({ length: 32 }, (_, i) => i);
+            const encodedKey = encodeRecoveryKey(key)!;
+
+            expect(decodeRecoveryKey(encodedKey)).toEqual(new Uint8Array(key));
+        });
+    });
+});