Implement getEncryptionInfoForEvent and deprecate getEventEncryptionInfo (#3693)

* Implement `getEncryptionInfoForEvent` and deprecate `getEventEncryptionInfo`

* fix tsdoc

* fix tests

* Improve test coverage

src/rust-crypto/rust-crypto.ts

@@ -39,6 +39,8 @@ import {
     CrossSigningStatus,
     CryptoCallbacks,
     DeviceVerificationStatus,
+    EventEncryptionInfo,
+    EventShieldColour,
     GeneratedSecretStorageKey,
     ImportRoomKeyProgressData,
     ImportRoomKeysOpts,
@@ -208,6 +210,11 @@ export class RustCrypto extends TypedEventEmitter<RustCryptoEvents, RustCryptoEv
         return await this.eventDecryptor.attemptEventDecryption(event);
     }
 
+    /**
+     * Implementation of (deprecated) {@link MatrixClient#getEventEncryptionInfo}.
+     *
+     * @param event - event to inspect
+     */
     public getEventEncryptionInfo(event: MatrixEvent): IEncryptedEventInfo {
         // TODO: make this work properly. Or better, replace it.
 
@@ -732,6 +739,16 @@ export class RustCrypto extends TypedEventEmitter<RustCryptoEvents, RustCryptoEv
         };
     }
 
+    /**
+     * Implementation of {@link CryptoApi.getEncryptionInfoForEvent}.
+     */
+    public async getEncryptionInfoForEvent(event: MatrixEvent): Promise<EventEncryptionInfo | null> {
+        return {
+            shieldColour: EventShieldColour.NONE,
+            shieldReason: null,
+        };
+    }
+
     /**
      * Returns to-device verification requests that are already in progress for the given user id.
      *