Improve Helm course

[pablosanchezpaz]

Motivation

We need a chart to show advanced techniques with helm.

Therefore:

1. This chart should have a service
2. A database is needed.
3. The chart should have secrets and configmaps to configure everything.
4. The chart should have tests.
5. The chart should have additional jobs to perform in a chron manner: i.e cronjobs.

Proposal

Write a chart that exposes a ghost service backed with a mariaDB database.

Everything should be configured using configmaps and secrets.

Additionally, we need a cronjob that, periodically dumps the database (mysql dump) every day.

[AinhoMD]

related to #163