asterisk: Create symlinks for each config individually

This commit refactors the way how configuration files are deployed to
the `/etc/asterisk` directory.

The current solution builds a Nix derivation containing all config files
and symlinks it to `/etc/asterisk`. The problem with that approach is
that it is not possible to provide additional configuration that should
not be written to the Nix store, i.e. files containing credentials.

The proposed solution changes the creation of configuration files so
that each configuration file gets symlinked to `/etc/asterisk`
individually so that it becomes possible to provide additional config
files to `/etc/asterisk` as well.

nixos/modules/services/networking/asterisk.nix

@@ -14,28 +14,9 @@ let
 
   # Add filecontents from files of useTheseDefaultConfFiles to confFiles, do not override
   defaultConfFiles = subtractLists (attrNames cfg.confFiles) cfg.useTheseDefaultConfFiles;
-  allConfFiles =
-    cfg.confFiles //
-    builtins.listToAttrs (map (x: { name = x;
-                                    value = builtins.readFile (cfg.package + "/etc/asterisk/" + x); })
-                              defaultConfFiles);
-
-  asteriskEtc = pkgs.stdenv.mkDerivation
-  ((mapAttrs' (name: value: nameValuePair
-        # Fudge the names to make bash happy
-        ((replaceChars ["."] ["_"] name) + "_")
-        (value)
-      ) allConfFiles) //
-  {
-    confFilesString = concatStringsSep " " (
-      attrNames allConfFiles
-    );
-
-    name = "asterisk-etc";
-
+  allConfFiles = {
     # Default asterisk.conf file
-    # (Notice that astetcdir will be set to the path of this derivation)
-    asteriskConf = ''
+    "asterisk.conf".text = ''
       [directories]
       astetcdir => /etc/asterisk
       astmoddir => ${cfg.package}/lib/asterisk/modules
@@ -48,43 +29,28 @@ let
       astrundir => /run/asterisk
       astlogdir => /var/log/asterisk
       astsbindir => ${cfg.package}/sbin
+      ${cfg.extraConfig}
     '';
-    extraConf = cfg.extraConfig;
 
     # Loading all modules by default is considered sensible by the authors of
     # "Asterisk: The Definitive Guide". Secure sites will likely want to
     # specify their own "modules.conf" in the confFiles option.
-    modulesConf = ''
+    "modules.conf".text = ''
       [modules]
       autoload=yes
     '';
 
     # Use syslog for logging so logs can be viewed with journalctl
-    loggerConf = ''
+    "logger.conf".text = ''
       [general]
 
       [logfiles]
       syslog.local0 => notice,warning,error
     '';
+  } //
+    mapAttrs (name: text: { inherit text; }) cfg.confFiles //
+    listToAttrs (map (x: nameValuePair x { source = cfg.package + "/etc/asterisk/" + x; }) defaultConfFiles);
 
-    buildCommand = ''
-      mkdir -p "$out"
-
-      # Create asterisk.conf, pointing astetcdir to the path of this derivation
-      echo "$asteriskConf" | sed "s|@out@|$out|g" > "$out"/asterisk.conf
-      echo "$extraConf" >> "$out"/asterisk.conf
-
-      echo "$modulesConf" > "$out"/modules.conf
-
-      echo "$loggerConf" > "$out"/logger.conf
-
-      # Config files specified in confFiles option override all other files
-      for i in $confFilesString; do
-        conf=$(echo "$i"_ | sed 's/\./_/g')
-        echo "''${!conf}" > "$out"/"$i"
-      done
-    '';
-  });
 in
 
 {
@@ -209,7 +175,9 @@ in
   config = mkIf cfg.enable {
     environment.systemPackages = [ cfg.package ];
 
-    environment.etc.asterisk.source = asteriskEtc;
+    environment.etc = mapAttrs' (name: value:
+      nameValuePair "asterisk/${name}" value
+    ) allConfFiles;
 
     users.users.asterisk =
       { name = asteriskUser;