[zabbix-community/zabbix] External Databases

[seanfariacustomink]

Allow Zabbix to connect to external databases (MySQL, PostgreSQL, MariaDB) via "values.yaml" and disable PostgreSQL DB creation.

[aeciopires]

This issue is related with #18

[xeberth]

Our company is migrating most of its workloads to kubernetes, including zabbix.

In terms of offering a robust HA monitoring service, external database support is business critical. It allows us to connect self-managed AWS RDS databases that offer HA