Switch to use bitnami mariadb repo

Good addition to your project would be switch to bitnami mariadb instead of provisioning it on your own. It's standard practice among big project, for example sonarqube, which uses bitnami's Postgresql:
https://github.com/SonarSource/helm-chart-sonarqube/blob/master/charts/sonarqube/Chart.yaml

It will make deployment more flexible