Knotx/knotx-example-project#58 refactor OAuth2 security

[Mateusz512]

Refactor OAuth2 tutorial to use OOTB Vert.x implementation of OAuth2 flow

Description

The routing logic has been moved to correct security logic and now uses OOTB Vert.x stuff.

Motivation and Context

In previous approach, the OAuth2 flow was mixed with business logic.

Screenshots (if appropriate)

Upgrade notes (if appropriate)

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.

---

I hereby agree to the terms of the Knot.x Contributor License Agreement.