Add a volume for /app/tmp/cache in 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

So that the application can write to it when the filesystem is otherwise readonly

Things to consider when reviewing

• 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?
• 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