treewide: make option examples constant

escape interpolations in examples, or replace them where they are not
useful.

nixos/modules/services/mail/rspamd.nix

@@ -5,6 +5,7 @@ with lib;
 let
 
   cfg = config.services.rspamd;
+  opt = options.services.rspamd;
   postfixCfg = config.services.postfix;
 
   bindSocketOpts = {options, config, ... }: {
@@ -285,8 +286,8 @@ in
               bindSockets = [{
                 socket = "/run/rspamd/rspamd.sock";
                 mode = "0660";
-                owner = "${cfg.user}";
-                group = "${cfg.group}";
+                owner = "''${config.${opt.user}}";
+                group = "''${config.${opt.group}}";
               }];
             };
             controller = {

nixos/modules/services/misc/matrix-synapse.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.matrix-synapse;
+  opt = options.services.matrix-synapse;
   pg = config.services.postgresql;
   usePostgresql = cfg.database_type == "psycopg2";
   logConfigFile = pkgs.writeText "log_config.yaml" cfg.logConfig;
@@ -197,7 +198,7 @@ in {
       tls_certificate_path = mkOption {
         type = types.nullOr types.str;
         default = null;
-        example = "${cfg.dataDir}/homeserver.tls.crt";
+        example = "/var/lib/matrix-synapse/homeserver.tls.crt";
         description = ''
           PEM encoded X509 certificate for TLS.
           You can replace the self-signed certificate that synapse
@@ -209,7 +210,7 @@ in {
       tls_private_key_path = mkOption {
         type = types.nullOr types.str;
         default = null;
-        example = "${cfg.dataDir}/homeserver.tls.key";
+        example = "/var/lib/matrix-synapse/homeserver.tls.key";
         description = ''
           PEM encoded private key for TLS. Specify null if synapse is not
           speaking TLS directly.
@@ -218,7 +219,7 @@ in {
       tls_dh_params_path = mkOption {
         type = types.nullOr types.str;
         default = null;
-        example = "${cfg.dataDir}/homeserver.tls.dh";
+        example = "/var/lib/matrix-synapse/homeserver.tls.dh";
         description = ''
           PEM dh parameters for ephemeral keys
         '';

nixos/modules/services/misc/sourcehut/builds.nix

@@ -63,7 +63,7 @@ in
               rev = "ff96a0fa5635770390b184ae74debea75c3fd534";
               ref = "nixos-unstable";
           };
-          image_from_nixpkgs = pkgs_unstable: (import ("${pkgs.sourcehut.buildsrht}/lib/images/nixos/image.nix") {
+          image_from_nixpkgs = pkgs_unstable: (import ("''${pkgs.sourcehut.buildsrht}/lib/images/nixos/image.nix") {
             pkgs = (import pkgs_unstable {});
           });
         in

nixos/modules/services/networking/jibri/default.nix

@@ -132,7 +132,7 @@ in
         pkgs.writeScript "finalize_recording.sh" ''''''
         #!/bin/sh
         RECORDINGS_DIR=$1
-        ${pkgs.rclone}/bin/rclone copy $RECORDINGS_DIR RCLONE_REMOTE:jibri-recordings/ -v --log-file=/var/log/jitsi/jibri/recording-upload.txt
+        ''${pkgs.rclone}/bin/rclone copy $RECORDINGS_DIR RCLONE_REMOTE:jibri-recordings/ -v --log-file=/var/log/jitsi/jibri/recording-upload.txt
         exit 0
         '''''';
       '';