Add documentation for Maintenance Mode and Health Checks in Front-Commerce

[paul-vd]

The changes introduce comprehensive documentation for the Maintenance Mode and Health Checks features in Front-Commerce. This includes:

1. A new section on Global Services, explaining their lifecycle and providing references to the RateLimiter and MaintenanceMode services.
2. Detailed guides on how to automatically detect service health and place the site in maintenance mode, including how to add health checks and configure their intervals.
3. Instructions on how to manually enter and exit maintenance mode using the Maintenance Mode API, including setting up authorization tokens and bypassing maintenance mode for specific IP addresses.
4. Updates to the defineExtension API reference to include new lifecycle hooks onServerInit and onServerServicesInit.
5. Configuration options for customizing the Maintenance Mode service in the front-commerce.config.ts file.
6. A new category in the documentation specifically for Maintenance Mode, making it easier for users to find relevant information.

• https://deploy-preview-917--heuristic-almeida-1a1f35.netlify.app/docs/3.x/category/maintenance-mode
• https://deploy-preview-917--heuristic-almeida-1a1f35.netlify.app/docs/3.x/api-reference/front-commerce-core/services
• https://deploy-preview-917--heuristic-almeida-1a1f35.netlify.app/docs/3.x/api-reference/front-commerce-core/config#maintenance

[linear]

FC-2251 Maintenance mode: detect remote service failures

[netlify]

👷 Deploy Preview for heuristic-almeida-1a1f35 processing.

Name	Link
🔨 Latest commit	c2947de
🔍 Latest deploy log	https://app.netlify.com/sites/heuristic-almeida-1a1f35/deploys/66759878850bb00008d7d039

[real34]

Nice docs!
Thanks.

Unless you want me to, I don't think it's necessary to do another review from me (hence the approval).