Use Stripe-side info when displaying webhook status

[annemirasol]

Instead of determining webhook status ('Enabled' vs 'Disabled') by using the presence or absence of secret keys, we check the actual status using Stripe API.

Fixes #3512

Changes proposed in this Pull Request:

In Stripe's Settings page, Account Status section, we display the webhook status as "Enabled" or "Disabled", based on the presence or absence of a webhook secret in the settings store. If the webhook has been disabled or deleted outside of WooCommerce, this approach leads to an inaccurate webhook status.

In this PR, we will display a more accurate webhook status by retrieving it using a Stripe API call.

Testing instructions

1. Set up a publicly accessible WooCommerce store, e.g. using tunneling via ngrok or JT, or upload this branch's build to a JN site.
2. Connect your store to your Stripe account.
3. On successfully connecting, you should see the webhook status as "Enabled".
4. Go to https://dashboard.stripe.com/test/webhooks, making sure you're on the correct Stripe account and mode (test/live). You should see the webhook for your store.
5. Click on the webhook to load its details page.
6. On the upper right corner, you should see a three-dot menu. Disable the webhook.
7. Go back to your WooCommerce store, and reload the Stripe settings page.
8. In develop, the webhook status still shows as Enabled.
9. In this branch, the webhook status now shows Disabled.

---

• Covered with tests (or have a good reason not to test in description ☝️)
• Added changelog entry in both changelog.txt and readme.txt (or does not apply)
• Tested on mobile (or does not apply)

Post merge

• Added testing instructions to the Release Testing Instructions wiki page (or does not apply)
• Added the needs docs label (or does not apply)
• Included this PR in the Release Thread scope (or does not apply)

[Mayisha]

The code looks good and it is working perfectly.
I have tested by enabling/disabling the webhook in my Stripe dashboard. 🎉

I noticed one thing. On every page refresh we are fetching the webhook status from Stripe. Also on every save on the Stripe settings page (i.e enable/disable any method and save), we are fetching this from Stripe again.
Should we opt for a short term caching for this webhook status response? Similar to how we cache the account data for about 2 hours.

[annemirasol]

Should we opt for a short term caching for this webhook status response? Similar to how we cache the account data for about 2 hours.

Good idea. I'll try to work that in for this PR.

[annemirasol]

@Mayisha Caching added in 2bbe8df, thanks for suggesting that.

• Cache is invalidated and API calls are made on page refresh, same behavior as account data.
• API calls are no longer made when saving.

[Mayisha]

Thanks for the changes @annemirasol. It is working nicely. 🎉

✅ Fetching the webhook status via API call on page refresh.
✅ Returning the data from the cache on any changes in the settings.