Add support for JSON.MSET (#2605)

* Added MSET command

MSET command added. Requires all keys to have the same JSON Path, which might fit most use cases, but is a limitation.  Optionally we could make the path an array as well to support all use cases.

* change JSON.MSET signature, add to json command object, fix tests

* its `item.value`, not `item.json`..

* Update MSET.ts

Removed unused RedisCommandArguments

---------

Co-authored-by: Leibale Eidelman <me@leibale.com>

packages/json/lib/commands/MSET.ts

@@ -0,0 +1,28 @@
+import { RedisJSON, transformRedisJsonArgument } from '.';
+import { RedisCommandArgument } from '@redis/client/dist/lib/commands';
+
+export const FIRST_KEY_INDEX = 1;
+
+interface JsonMSetItem {
+    key: RedisCommandArgument;
+    path: RedisCommandArgument;
+    value: RedisJSON;
+}
+
+export function transformArguments(items: Array<JsonMSetItem>): Array<string> {
+  
+    const args = new Array(1 + items.length * 3);
+    args[0] = 'JSON.MSET';
+
+    let argsIndex = 1;
+    for (let i = 0; i < items.length; i++) {
+        const item = items[i];
+        args[argsIndex++] = item.key;
+        args[argsIndex++] = item.path;
+        args[argsIndex++] = transformRedisJsonArgument(item.value);
+    }
+
+    return args;
+}
+
+export declare function transformReply(): 'OK';