Implement option contextualConsentOnly

We need this for handling Drupal CMS AI features.

I added optional textfield and option contextualConsentOnly for better handling of contextual consents.

For testing you should apply #3491906 before.

This looks great. Just one question, but still RTBC otherwise:

The setting contextual_consent_only doesn't seem to be used anywhere. Is this baked into the upstream library? But even then, the value should at least be forwarded, or am I missing something?

Yes, the effect of this flag is less than expected:

This service is not activated when “Accept all” is clicked (only relevant if this button is activated in the module settings).

Thank you all for review and feedback. It is a pleasant journey with you to the stable version.