[ADR] Select a backup solution for SonarQube

[Racer159]

Is your feature request related to a problem? Please describe.

As Ashton I want to be able to backup SonarQube safely so that I can restore it easily in the event of a disaster.

Describe the solution you'd like

We should identify and select solutions that are able to backup the SonarQube database, and then follows the recommendations for restoration:

https://docs.sonarsource.com/sonarqube/9.6/instance-administration/backup-and-restore/

These should be written in a simple ADR to capture why the final solution was chosen and a follow on implementation issue should be created.

Additional context

We currently don't have set SLAs but should target a baseline to have something while we continue to experiment.

[zachariahmiller]

https://docs.sonarsource.com/sonarqube/latest/instance-administration/backup-and-restore/

In the absence of more specific guidance, use normal rds backup/restore practices