PostgreSQL migration

[SirNoob97]

Create a to-do list for the following requirements.

• Refactoryze entities.
• Refactorize test configuration for postgres.
• Add Postgres healthcheck in the docker-compose file.
• SQL script for init the DB to discard dummy-data and avoid hibernate interventions.
• repository function findbyEmail #25
• service function get post by id #26
• service get all posts #27

[SirNoob97]

I will work on this