feat(crud-master): add basic and incomplete subject

subjects/devops/crud_master/README.md

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+## CRUD Master
+
+### Instructions
+
+APIs are a very common and convenient way to deploy services in a modular way.
+In this exercise we will create a simple API infrastructure, having an API gateway connected with two other APIs.
+Those two APIs will in turn get data from two distinct databases.
+The communication between APIs will be done by using HTTP and message queuing systems.
+All those services will be in turn encapsulated in different virtual machines.
+
+#### General overview
+
+We will setup an e-commerce system, where one API (`inventory`) will take track of the orders and another one (`billing`) will process the payments.
+
+The API gateway will communicate in HTTP with `inventory` and using RabbitMQ for `billing`.
+
+#### API 1: Inventory
+
+#### API 2: Billing
+
+#### The API Gateway
+