feat: Add final parameter to onConsentChange

[zekehuntergreen]

What does this change?

• adds an optional final parameter to onConsentChange which defaults to false. When a true value is passed, the callback is pushed onto a new finalCallbackQueue. The finalCallbackQueue's callbacks are guaranteed to execute after the default callBackQueue's when consent state changes.

Why?

• In Add reload on consent change frontend#25409 we use onConsentChange to register a callback that reloads the page when consent state changes from a state where the user has accepted targeted advertising to one which rejects it or vice versa.
• reloading the page as part of an onConsentChange callback opens up the possibility of overriding other uses of onConsentChange whose callbacks won't have time to execute before the page is reloaded. This could cause bugs that are very difficult to track down.
• Another approach considered was to wrap Add reload on consent change frontend#25409 's callback in Promise.resolve().then and / or setTimeout so that the callback that reloads the page is put on the microtask queue or task queue respectively. This would increase the probability but not guarantee that other callbacks registered with onConsentChange could execute before the page is reloaded.

[Mark-McCracken]

According to @sookburt , @theemilyturner asked Susan Bingham about whether we should reload the page for a consent change, and the answer was no, so this is no longer relevant.
If no-one has anything to say to the contrary, and if still open in a week, we'll close this.

[Mark-McCracken]

as evidenced here: https://trello.com/c/sqmNkN20

[sookburt]

This might need to be resurrected as part of the cookie deny list changes.

[changeset-bot]

🦋 Changeset detected

Latest commit: ad2e8ad

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@guardian/consent-management-platform	Minor

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[github-actions]

Deploy build 1909 of consent::cmp-monitoring to CODE

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[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟢	Statements	92.81% (+0.11% 🔼)	258/278
🟢	Branches	83.9% (+0.42% 🔼)	99/118
🟢	Functions	90%	63/70
🟢	Lines	92.59% (+0.11% 🔼)	250/270

Test suite run success

331 tests passing in 16 suites.

Report generated by 🧪jest coverage report action from ad2e8ad

[github-actions]

🚀 0.0.0-beta-20240124124059 published to npm as a beta release

[github-actions]

🚀 0.0.0-beta-20240206103322 published to npm as a beta release

[github-actions]

🚀 0.0.0-beta-20240207101556 published to npm as a beta release

[github-actions]

🚀 0.0.0-beta-20240213105136 published to npm as a beta release

[akinsola-guardian]

Thanks for this. This was tested in CODE and worked as expected.