RGA Customer Module

##Scenario An insurance company needs a system to manage their customer data. A software engineering team is working on the story below.

As a system user, I want to add new customer data into the system. After added, I can view a certain customer, and a customer list. Of course, I am also able to modify the data as well as remove it from the system.

##Instructions You are required to provide the functions of:

1. Creating a single customer
2. Updating a single customer
3. Deleting a single customer
4. Reading a single customer
5. Listing all customers
6. Authentication (assume that the system user is existing) 6-1. Login - getting a login token. 6-2. Logout - destroying a login token.

Except for point 6, those functions(end-points) should be secured, which need a credential to access.

Please implement it in Java. Any frameworks are accepted.

##Acceptance criteria

1. RESTful APIs
2. JSON request and response
3. Evidence of a BDD/TDD approach
4. Clean, maintainable code adhering to SOLID principles