Webhook not setup banner

Created by: malomarrec

User problem

Nearly every new customer contacts support, reporting that their changesets are not syncing. In the vast majority of cases, their site admin has not setup webhooks. Even some older customers still have not setup webhooks, resulting in degraded performance, and changesets taking up to 8 hours to update versus updating nearly immediately with webhooks.

Users report not knowing about webhooks, or forgetting to set them up. Once instructed to do so, customers successfully setup notebooks. The webhook setup flow is not great, and we have a proposal to fix it, but the primary root cause is that site admins don't know about webhooks.

Proposed change

Figma | Draft docs page https://github.com/sourcegraph/sourcegraph/pull/25558

If webhooks are not setup for any given codehost connected to the instance:

• non site admin users see a banner on batch changes pages, informing them that changesets are likely not up to date because webhooks are not setup. This banner points to the webhooks docs page, which explains to users they need to ask a site-admin to setup webhooks.

• site admin get a banner, with a link to the docs, and a list of codehosts to configure linking to the codehost config page

• site admins can explicitly opt-out of the webhooks warning for a codehost (in case some organisations have policies against webhooks), by setting a site admin flag. In that case, the banner doesn't show anymore for any user.

• regardless of site admin settings, users see additional hints if webhooks are not setup