docs: Update info about metrics for 2.6

Also add events.handlers namespace and fix dhall link.

src/docs/markdown/caddyfile/directives/metrics.md

@@ -5,7 +5,7 @@ title: metrics (Caddyfile directive)
 # metrics
 
 Configures a Prometheus metrics exposition endpoint so the gathered metrics can
-be exposed for scraping.
+be exposed for scraping. **Metrics must be [turned on in your global options](/docs/caddyfile/options#metrics) first.**
 
 Note that a `/metrics` endpoint is also attached to the [admin API](/docs/api),
 which is not configurable, and is not available when the admin API is disabled.

src/docs/markdown/caddyfile/options.md

@@ -105,6 +105,7 @@ Possible options are:
 			write       <duration>
 			idle        <duration>
 		}
+		metrics
 		max_header_size <size>
 		log_credentials
 		protocols [h1|h2|h2c|h3]
@@ -381,6 +382,11 @@ listener_wrappers {
 - **idle** is a [duration value](/docs/conventions#durations) that sets the maximum time to wait for the next request when keep-alives are enabled. Defaults to 5 minutes to help avoid resource exhaustion.
 
 
+##### `metrics`
+
+Enables Prometheus metrics collection; necessary before scraping metrics. Note that metrics reduce performance on really busy servers. (Our community is working on improving this. Please get involved!)
+
+
 ##### `max_header_size`
 
 The maximum size to parse from a client's HTTP request headers. It accepts all formats supported by [go-humanize](https://github.com/dustin/go-humanize/blob/master/bytes.go).

src/docs/markdown/config-adapters.md

@@ -20,7 +20,7 @@ The following config adapters are currently available (some are third-party proj
 - [**cue**](https://github.com/caddyserver/cue-adapter)
 - [**toml**](https://github.com/awoodbeck/caddy-toml-adapter)
 - [**hcl**](https://github.com/francislavoie/caddy-hcl)
-- [**dhall**](https://github.com/mholt/caddy-dhall)
+- [**dhall**](https://github.com/mholt/dhall-adapter)
 
 ## Using config adapters
 

src/docs/markdown/extending-caddy/namespaces.md

@@ -19,6 +19,7 @@ caddy.fs  | [`fs.FS`](https://pkg.go.dev/io/fs#FS) | Virtual file system |  <i>
 caddy.logging.encoders.filter | [`logging.LogFieldFilter`](https://pkg.go.dev/github.com/caddyserver/caddy/v2/modules/logging?tab=doc#LogFieldFilter) | Log field filter</i>
 caddy.logging.writers | [`caddy.WriterOpener`](https://pkg.go.dev/github.com/caddyserver/caddy/v2?tab=doc#WriterOpener) | Log writers
 caddy.storage | [`caddy.StorageConverter`](https://pkg.go.dev/github.com/caddyserver/caddy/v2?tab=doc#StorageConverter) | Storage backends
+events.handlers | [`caddyevents.Handler`](https://pkg.go.dev/github.com/caddyserver/caddy/v2/modules/caddyevents#Handler) | Event handlers | <i>⚠️ Experimental</i>
 http.authentication.hashes | [`caddyauth.Comparer`](https://pkg.go.dev/github.com/caddyserver/caddy/v2/modules/caddyhttp/caddyauth?tab=doc#Comparer) | Password hashers/comparers
 http.authentication.providers | [`caddyauth.Authenticator`](https://pkg.go.dev/github.com/caddyserver/caddy/v2/modules/caddyhttp/caddyauth?tab=doc#Authenticator) | HTTP authentication providers
 http.handlers | [`caddyhttp.MiddlewareHandler`](https://pkg.go.dev/github.com/caddyserver/caddy/v2/modules/caddyhttp?tab=doc#MiddlewareHandler) | HTTP handlers
@@ -32,3 +33,5 @@ tls.handshake_match | [`caddytls.ConnectionMatcher`](https://pkg.go.dev/github.c
 tls.issuance | [`certmagic.Issuer`](https://pkg.go.dev/github.com/caddyserver/certmagic?tab=doc#Issuer) | TLS certificate issuer<br>
 tls.get_certificate | [`certmagic.CertificateManager`](https://pkg.go.dev/github.com/caddyserver/certmagic?tab=doc#CertificateManager) | TLS certificate manager | <i>⚠️ Experimental</i>
 tls.stek | [`caddytls.STEKProvider`](https://pkg.go.dev/github.com/caddyserver/caddy/v2/modules/caddytls?tab=doc#STEKProvider) | TLS session ticket key source</i>
+
+Namespaces marked as "Experimental" are subject to change. (Please develop with them so we can finalize their interfaces!)

src/docs/markdown/metrics.md

@@ -9,6 +9,20 @@ Caddy server on an embedded device, it's likely that at some point you'll want
 to have a high-level overview of what Caddy is doing, and how long it's taking.
 In other words, you're going to want to be able to _monitor_ Caddy.
 
+## Enabling metrics
+
+You'll need to turn metrics on. If using a Caddyfile, enable metrics [in global options](/docs/caddyfile/options#metrics):
+
+```caddy
+{
+    servers {
+        metrics
+    }
+}
+```
+
+If using JSON, enable metrics in your [server configuration](/docs/json/apps/http/servers/) by adding `"metrics": {}`.
+
 ## Prometheus
 
 [Prometheus](https://prometheus.io) is a monitoring platform that collects