DOC/MINOR: metrics: add HTTPS warning notes to metrics documentation

Add important notes to metrics.md, metrics-basic.md, and metrics-kube-rbac.md to clarify that switching from the default "none" mode to "basic" or "kube-rbac" changes the metrics endpoint protocol from HTTP to HTTPS. This helps users avoid connection errors by reminding them to explicitly update their curl commands and Prometheus scrape configurations to use the https:// scheme.

Author: oktalz

documentation/metrics-basic.md

@@ -5,6 +5,10 @@ Credentials are provided via CLI flags or environment variables.
 
 The endpoint is served over HTTPS with an auto-generated self-signed certificate.
 
+> **Important:** This mode serves metrics over **HTTPS** (not HTTP). If you are switching from the
+> default `none` mode, you must use `https://` in your curl commands and Prometheus scrape configs.
+> Using `http://` will result in: *"Client sent an HTTP request to an HTTPS server."*
+
 ## When to Use
 
 - External Prometheus instances scraping from outside the cluster

documentation/metrics-kube-rbac.md

@@ -6,6 +6,10 @@ only ServiceAccounts with the correct RBAC permissions can access `/metrics`.
 
 The endpoint is served over HTTPS with an auto-generated self-signed certificate.
 
+> **Important:** This mode serves metrics over **HTTPS** (not HTTP). If you are switching from the
+> default `none` mode, you must use `https://` in your curl commands and Prometheus scrape configs.
+> Using `http://` will result in: *"Client sent an HTTP request to an HTTPS server."*
+
 ## When to Use
 
 - Production environments

documentation/metrics.md

@@ -30,6 +30,10 @@ All flags can also be set via environment variables (e.g., `METRICS_AUTH=basic`)
 
 Both `kube-rbac` and `basic` modes automatically enable HTTPS with a self-signed certificate.
 
+> **Note:** Switching from `none` to `basic` or `kube-rbac` changes the protocol from HTTP to HTTPS.
+> You must update your curl commands (use `https://` and `-k` for self-signed certs) and Prometheus
+> scrape configs (set `scheme: https` with `insecure_skip_verify: true`) accordingly.
+
 For detailed setup instructions, see:
 - [metrics-none.md](metrics-none.md) - No authentication (default)
 - [metrics-kube-rbac.md](metrics-kube-rbac.md) - Kubernetes RBAC authentication