Not able to add CSP Headers with single quotes

**Issue**
We are not able to add CSP headers that contains single quotes. Example:
nginx.ingress.kubernetes.io/configuration-snippet: >
more_set_headers "Content-Security-Policy: upgrade-insecure-requests;default-src 'self';" ;
...

I did remove ' from annotation-value-word-blocklist in nginx configmap, but it keeps getting reverted to default values after restarting nginx deployment.

I do understand single quote is blocked because of security, but, I couldn't find another way to add CSP header.

Proposal
We should be able to overwrite nginx configmap.

Start with the handling of the nginx.ingress.kubernetes.io/configuration-snippet annotation and the annotation-value-word-blocklist configuration during nginx deployment restarts. Trace why a customized nginx configmap is replaced by defaults; done means a supported override persists and CSP headers containing single quotes can be configured safely, with the relevant behavior covered by tests.

Written by the indexing model from the issue text.