Version handle the API

[m-linner-ericsson]

Description

Introduce version handling of the API

Also, see #427 in the backend

Motivation

By version handling, the API users can upgrade EI without having to change their code. The user can switch to the new API when they have the possibility.

Exemplification

Here you can read briefly about API versioning:
https://restfulapi.net/versioning/

The most common way is to append /v1 at the root path.

Benefits

By version handling the API, it will be backward compatible.

Possible Drawbacks