Add volume hints to the Dockerfile

[AP-Hunt]

What problem does this pull request solve?

Trello card: https://trello.com/c/KoHvaEUA/681-aws-m112-ecs-read-only-root-filesystem-configuration

We can use VOLUME instructions in our Dockerfile to instruct the runtime to create a mount point for an external volume.

When AWS ECS sees the instruction (from the built container), it automatically attaches ephemeral storage at that location [1]. This is useful for us because we want to enable read only root filesystems, but the applications still need to be able to write to a small portion of it. We can achieve that by mounting ephemeral storage atop the paths it needs to write to.

[1] https://docs.aws.amazon.com/AmazonECS/latest/developerguide/bind-mounts.html#bind-mount-considerations

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• Ensure that you consider the wider context.
• Does it work when run on your machine?
• Is it clear what the code is doing?
• Do the commit messages explain why the changes were made?
• Are there all the unit tests needed?
• Do the end to end tests need updating before these changes will pass?
• Has all relevant documentation been updated?

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sarahseewhy]

Thank you 🥇 !