feat: split out docker build #440

Job	Run time
Build, stable, linux/amd64	2m 49s
Build, stable, linux/arm64	17m 1s
Anchore Container Scan	1m 17s
Test basic, stable	3m 7s
Trivy Container Scan	1m 59s
Test split, stable	2m 49s
Test SAML, stable	2m 19s
Test novolume, stable	3m 21s
Test single celery process, stable	2m 38s
Test SSL, stable	2m 12s
Merge images	36s
Publish to Docker Hub, stable	0s
Publish to GitHub, stable	0s
Create release on GitHub	0s
	40m 8s

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