Restructure file validation code #15016

Job	Run time
End-to-end tests, chromium	13m 30s
Run the Django test suite	7m 53s
Set up docker build 'dynamic' env variables	1s
End-to-end tests, firefox	16m 46s
End-to-end tests, webkit	12m 15s
Run the Django test suite in reverse	5m 26s
Build and check documentation	3m 58s
docker_build (extensions, token_exchange,prefill_haalcentraalhr, all-extensions-) / Build image	2m 54s
docker_build (production) / Build image	2m 46s
Scan docker image	2m 25s
Simulate upgrading instances (2.8.2)	1m 30s
Check for unexepected OAS changes	4s
Generate Postman collection from OAS	10s
Generate SDKs from OAS	35s
Validate OAS	16s
Push Docker image	0s
update-docker-readme	0s
	1h 10m 29s

Provide feedback