docs: Document environment variables for config options

docs/configuration.mdx

@@ -37,6 +37,10 @@ # This maps to the `base_url` field of the `[global.antispam.draupnir]` section
 # Alternatively, you can pass a (quoted) struct to define an entire section
 # This maps to the [global.well_known] section
 CONTINUWUITY_WELL_KNOWN="{ client=https://example.com,server=example.com:443 }"
+
+# Options that take a list are written as a (quoted) array
+CONTINUWUITY_TRUSTED_SERVERS='["matrix.org"]'
+CONTINUWUITY_PORT='[8008, 8448]'
 ```
 
 ### Alternative prefixes

docs/deploying/kubernetes.mdx

@@ -79,7 +79,7 @@ # Continuwuity for Kubernetes
               value: "https://matrix.example.com"
             - name: CONTINUWUITY_ALLOW_REGISTRATION
               value: "false"
-            - name: RUST_LOG
+            - name: CONTINUWUITY_LOG
               value: info
           readinessProbe:
             httpGet:

src/macros/config.rs

@@ -89,6 +89,8 @@ fn generate_example(input: &ItemStruct, args: &[Meta], write: bool) -> Result<To
 		}
 	}
 
+	let env_prefix = env_prefix(section);
+
 	let mut summary: Vec<TokenStream2> = Vec::new();
 	let mut nested_displays: Vec<TokenStream2> = Vec::new();
 
@@ -144,6 +146,12 @@ fn generate_example(input: &ItemStruct, args: &[Meta], write: bool) -> Result<To
 					file.write_fmt(format_args!("\n{doc}"))
 						.expect("written to config file");
 
+					file.write_fmt(format_args!(
+						"# env: {env_prefix}{}\n",
+						ident.to_string().to_uppercase()
+					))
+					.expect("written to config file");
+
 					file.write_fmt(format_args!("#{ident} ={default}\n"))
 						.expect("written to config file");
 				}
@@ -213,6 +221,19 @@ fn fmt(&self, out: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
 	Ok(display)
 }
 
+fn env_prefix(section: &str) -> String {
+	let nested = section
+		.strip_prefix("global")
+		.unwrap_or(section)
+		.trim_start_matches('.');
+
+	if nested.is_empty() {
+		"CONTINUWUITY_".to_owned()
+	} else {
+		format!("CONTINUWUITY_{}__", nested.replace('.', "__").to_uppercase())
+	}
+}
+
 fn get_default(field: &Field) -> Option<String> {
 	for attr in &field.attrs {
 		let Meta::List(MetaList { path, tokens, .. }) = &attr.meta else {