Add support for T-Digest (#2214)

* wip

* close #2216 - add support for TDIGEST.MERGESTORE and make compression optional on TDIGEST.CREATE

* fix some tdigest commands, use bloom edge docker

* fix index.ts

* 2.4-RC2 (v2.4.1)

* fix some commands and tests

* clean code

packages/bloom/lib/commands/t-digest/MERGE.spec.ts

@@ -0,0 +1,50 @@
+import { strict as assert } from 'assert';
+import testUtils, { GLOBAL } from '../../test-utils';
+import { transformArguments, transformReply } from './MERGE';
+
+describe('TDIGEST.MERGE', () => {
+    describe('transformArguments', () => {
+        describe('srcKeys', () => {
+            it('string', () => {
+                assert.deepEqual(
+                    transformArguments('dest', 'src'),
+                    ['TDIGEST.MERGE', 'dest', '1', 'src']
+                );
+            });
+
+            it('Array', () => {
+                assert.deepEqual(
+                    transformArguments('dest', ['1', '2']),
+                    ['TDIGEST.MERGE', 'dest', '2', '1', '2']
+                );
+            });
+        });
+
+        it('with COMPRESSION', () => {
+            assert.deepEqual(
+                transformArguments('dest', 'src', {
+                    COMPRESSION: 100
+                }),
+                ['TDIGEST.MERGE', 'dest', '1', 'src', 'COMPRESSION', '100']
+            );
+        });
+
+        it('with OVERRIDE', () => {
+            assert.deepEqual(
+                transformArguments('dest', 'src', {
+                    OVERRIDE: true
+                }),
+                ['TDIGEST.MERGE', 'dest', '1', 'src', 'OVERRIDE']
+            );
+        });
+    });
+
+    testUtils.testWithClient('client.tDigest.merge', async client => {
+        const [ , reply ] = await Promise.all([
+            client.tDigest.create('src'),
+            client.tDigest.merge('dest', 'src')
+        ]);
+
+        assert.equal(reply, 'OK');
+    }, GLOBAL.SERVERS.OPEN);
+});