feat(coderd/database): track user status changes over time (#16019)

RE: https://github.com/coder/coder/issues/15740,
https://github.com/coder/coder/issues/15297

In order to add a graph to the coder frontend to show user status over
time as an indicator of license usage, this PR adds the following:

* a new `api.insightsUserStatusCountsOverTime` endpoint to the API
* which calls a new `GetUserStatusCountsOverTime` query from postgres
* which relies on two new tables `user_status_changes` and
`user_deleted`
* which are populated by a new trigger and function that tracks updates
to the users table

The chart itself will be added in a subsequent PR

---------

Co-authored-by: Mathias Fredriksson <mafredri@gmail.com>

coderd/coderd.go

@@ -1281,6 +1281,7 @@ func New(options *Options) *API {
 			r.Use(apiKeyMiddleware)
 			r.Get("/daus", api.deploymentDAUs)
 			r.Get("/user-activity", api.insightsUserActivity)
+			r.Get("/user-status-counts", api.insightsUserStatusCounts)
 			r.Get("/user-latency", api.insightsUserLatency)
 			r.Get("/templates", api.insightsTemplates)
 		})