Fix database container

• Make database container non-static

Replacing in memory for Postgres customer repository - Spring Boot from 2.5.6 to 2.6.1

List of changes

• Upgrade Spring Boot from 2.5.6 to 2.6.1
• Replacing in memory for Postgres customer repository
• Added Flyway and a first migration with creation of customer table
• Added docker compose file to run locally

Full Changelog: v1.0.0...v1.1.0

First release - Stable version

Full Changelog: https://github.com/Hyunk3l/hexagonal-architecture-kotlin-template/commits/v1.0.0