Support standard health check endpoint

[cruftex]

Describe the problem to be solved

I would like to include the application in our monitoring system.

Describe the solution you would like

Support standard health check endpoints, e.g. like the one defined by Kubernetes, (livez and readyz)
https://kubernetes.io/docs/reference/using-api/health-checks/

Alternatively it could be exposed via the API. Here is an example:
https://admin-docs.zammad.org/en/latest/system/monitoring.html

That should not be too difficult, maybe I am able to craft a PR based on what is already there in the admin section. Thoughts?

[paulfitz]

There is a /status endpoint, though I'm sure it could be elaborated and brought more into alignment with applicable standards.

grist-core/app/server/lib/FlexServer.ts

Lines 530 to 539 in a8c209b

	public addHealthCheck() {
	if (this._check('health')) { return; }
	// Health check endpoint. if called with /hooks, testing hooks are required in order to be
	// considered healthy. Testing hooks are used only in server started for tests, and
	// /status/hooks allows the tests to wait for them to be ready.
	// If db=1 query parameter is included, status will include the status of DB connection.
	// If redis=1 query parameter is included, status will include the status of the Redis connection.
	// If docWorkerRegistered=1 query parameter is included, status will include the status of the
	// doc worker registration in Redis.
	this.app.get('/status(/hooks)?', async (req, res) => {