CI/CD

fix: Export attachments url in proposal serializer #272

Job	Run time
Lint code	2m 30s
Tests (0-2)	3m 2s
System tests (0-4)	3m 2s
Test build docker image	3m 1s
Tests (1-2)	3m 2s
System tests (1-4)	3m 2s
TODO	6s
System tests (2-4)	2m 58s
System tests (3-4)	3m 4s
Check for Zeitwerk errors	2m 19s
Build and push image to Registry	1s
Generate release	1s
	26m 8s

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