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.spec.ts

@@ -0,0 +1,35 @@
+import { strict as assert } from 'assert';
+import testUtils, { GLOBAL } from '../test-utils';
+import { transformArguments } from './MSET';
+
+describe('MSET', () => {
+    it('transformArguments', () => {
+        assert.deepEqual(
+            transformArguments([{
+                key: '1',
+                path: '$',
+                value: 1
+            }, {
+                key: '2',
+                path: '$',
+                value: '2'
+            }]),
+            ['JSON.MSET', '1', '$', '1', '2', '$', '"2"']
+        );
+    });
+
+    testUtils.testWithClient('client.json.mSet', async client => {
+        assert.deepEqual(
+            await client.json.mSet([{
+                key: '1',
+                path: '$',
+                value: 1
+            }, {
+                key: '2',
+                path: '$',
+                value: '2'
+            }]),
+            'OK'
+        );
+    }, GLOBAL.SERVERS.OPEN);
+});