feature: the web service shows and changes the settings of the metrics service at /metrics/settings, and OpenVPN starts on a new router, as setup installs CRLs that revoke nothing.

README.md

@@ -1007,7 +1007,7 @@ curl http://10.0.0.4:7081/status
 
 ### Tokens and signing in
 
-`/config`, `/users`, `/service-accounts`, `/groups`, `/site-to-site`, `/backup`, `/remote-access`, `/ca`, `/logs`, `/sites`, `/dns`, `/shell` and `/account` need a JWT in an `Authorization: Bearer` header, signed with
+`/config`, `/metrics/history`, `/metrics/settings`, `/users`, `/service-accounts`, `/groups`, `/site-to-site`, `/backup`, `/remote-access`, `/ca`, `/logs`, `/sites`, `/dns`, `/shell` and `/account` need a JWT in an `Authorization: Bearer` header, signed with
 HS256 by the key the web service makes on its first run, `/etc/vpn-router/web.key` (root only).
 The key never leaves the router; while it does not exist these paths and `/auth` are not served
 (404). A missing, expired or wrongly signed token, or one of another algorithm, gets 401 with
@@ -1332,6 +1332,18 @@ The answer of `GET /backup` holds:
 
 A change is made, checked and applied as for `/site-to-site`.
 
+### The /metrics/settings API
+
+`/metrics/settings` shows and changes the settings of the metrics service, with the same token as
+`/users`.
+
+| Request | Body | Answer |
+| --- | --- | --- |
+| `GET /metrics/settings` | | `{"settings"}`: the `metrics` section without `otlp_password`, with `otlp_password_set` |
+| `PUT /metrics/settings` | any of the settings of the `metrics` section; an empty or absent `otlp_password` keeps the secret, and an empty `otlp_username` removes it | `{"settings"}` |
+
+A change is made, checked and applied as for `/site-to-site`.
+
 ### The /remote-access API
 
 `/remote-access` shows and changes the remote access systems, IKEv2 (`p2s`),