Documented /healthy, /ready and lifecycle API (#5737)

Signed-off-by: Marco Pracucci <marco.pracucci@spreaker.com>

docs/management_api.md

@@ -0,0 +1,50 @@
+---
+title: Management API
+sort_rank: 7
+---
+
+# Management API
+
+Prometheus provides a set of management API to ease automation and integrations.
+
+
+### Health check
+
+```
+GET /-/healthy
+```
+
+This endpoint always returns 200 and should be used to check Prometheus health.
+
+
+### Readiness check
+
+```
+GET /-/ready
+```
+
+This endpoint returns 200 when Prometheus is ready to serve traffic (i.e. respond to queries).
+
+
+### Reload
+
+```
+PUT  /-/reload
+POST /-/reload
+```
+
+This endpoint triggers a reload of the Prometheus configuration and rule files. It's disabled by default and can be enabled via the `--web.enable-lifecycle` flag.
+
+An alternative way trigger a configuration reload is by sending a `SIGHUP` to the Prometheus process.
+
+
+### Quit
+
+```
+PUT  /-/quit
+POST /-/quit
+```
+
+This endpoint triggers a graceful shutdown of Prometheus. It's disabled by default and can be enabled via the `--web.enable-lifecycle` flag.
+
+An alternative way trigger a graceful shutdown is by sending a `SIGTERM` to the Prometheus process.

docs/migration.md

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 ---
 title: Migration
-sort_rank: 7
+sort_rank: 8
 ---
 
 # Prometheus 2.0 migration guide

docs/stability.md

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 ---
 title: API Stability
-sort_rank: 8
+sort_rank: 9
 ---
 
 # API Stability Guarantees