Add support for redis functions (#2020)

* fix #1906 - implement BITFIELD_RO

* initial support for redis functions

* fix test utils

* redis functions commands and tests

* upgrade deps

* fix "Property 'uninstall' does not exist on type 'SinonFakeTimers'"

* upgrade dockers version

* Merge branch 'master' of github.com:redis/node-redis into functions

* fix FUNCTION LIST WITHCODE and FUNCTION STATS

* upgrade deps

* set minimum version for FCALL and FCALL_RO

* fix FUNCTION LOAD

* FUNCTION LOAD

* fix FUNCTION LOAD & FUNCTION LIST & FUNCTION LOAD WITHCODE

* fix FUNCTION_LIST_WITHCODE test

packages/client/lib/commands/FUNCTION_FLUSH.spec.ts

@@ -0,0 +1,30 @@
+import { strict as assert } from 'assert';
+import testUtils, { GLOBAL } from '../test-utils';
+import { transformArguments } from './FUNCTION_FLUSH';
+
+describe('FUNCTION FLUSH', () => {
+    testUtils.isVersionGreaterThanHook([7, 0]);
+
+    describe('transformArguments', () => {
+        it('simple', () => {
+            assert.deepEqual(
+                transformArguments(),
+                ['FUNCTION', 'FLUSH']
+            );
+        });
+
+        it('with mode', () => {
+            assert.deepEqual(
+                transformArguments('SYNC'),
+                ['FUNCTION', 'FLUSH', 'SYNC']
+            );
+        });
+    });
+
+    testUtils.testWithClient('client.functionFlush', async client => {
+        assert.equal(
+            await client.functionFlush(),
+            'OK'
+        );
+    }, GLOBAL.SERVERS.OPEN);
+});