feat: add usecase Pub-sub

Author: Skippia

.gitignore

@@ -1 +1,2 @@
 **/node_modules
+**/dist

Nest-microservices/.gitignore

@@ -0,0 +1,27 @@
+## Subscriber, Publisher
+1. Establish connection to the RabbitMQ
+2. Create a channel with RabbitMQ
+3. Create or connect to exchange - await `channel.assertExchange`('name_exchange', 'type_exchange', options)
+
+## Subscriber
+4. Create a queue  - await `channel.assertQueue`('queue_id', options)
+5. Bind this queue to exchange (await `channel.bindQueue`('queue_id', 'exchange_name', 'event_name'))
+6. Start to consume messages from queue - `channel.consume`('queue_id', cb)
+7. If we get message and this message requires of acknowledgement - send message to this replyQueue:
+    - `channel.sendToQueue`('reply_to_queue', some_data, {correlationId: message.fields.correlationId})
+
+## Publisher
+4. Create a replyQueue - await `channel.assertQueue`('', { exclusive: true })
+5. Start to consume messages from replyQueue - `channel.consume`('queue_id', cb)
+6. Send message to exchange:
+    - `channel.publish`('name_exchange', 'event_name', message, {replyTo: 'reply_queue_id', correlationId: string }) 
+	
+
+## How does it work?
+- [Publisher]: Send a message to the exchange
+- [Exchange]: Gets this message and redirects to the subscriber
+- [Subscriber]: Check if there is replyTo option and it that is case - reply to this queue
+- [Publisher]: Gets message from the replyQueue
+
+
+![alt text](./schema.png)

Pub-sub/README.md

@@ -0,0 +1,8 @@
+version: "3"
+services:
+  rabbitmq:
+    image: rabbitmq:3-management
+    restart: always
+    ports:
+      - '15672:15672'
+      - '5672:5672'

Pub-sub/docker-compose.yml

@@ -0,0 +1,18 @@
+{
+  "name": "rmq-demo",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "amqplib": "^0.9.0"
+  },
+  "devDependencies": {
+    "@types/amqplib": "^0.8.2",
+    "@types/node": "^17.0.32"
+  }
+}