feat: exit on SIGTERM signal

[daniel-mader]

Description of change

The application should handle SIGTERM commands and exit immediately. SIGTERM is currently unhandled and thus Kubernetes waits for 30 seconds, before it forcefully terminates the container. Graceful shutdowns are contrary to Crash-only design, so graceful shutdowns (clean up, flush messages, properly close connections) can not always be expected anyway.

Links to any relevant issues

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How the change has been tested

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Definition of Done checklist

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• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have successfully tested this change in a docker environment

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 21 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
agent_application/src/lib.rs	0.00%	21 Missing ⚠️

Files with missing lines	Coverage Δ
agent_application/src/lib.rs	0.00% <0.00%> (ø)

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