programs.khal: add "addresses" option + tidy up (#5221)

- Add `accounts.<calendar|contact>.accounts.<name>.khal.addresses`
  option to enable new configuration option, "addresses", from khal,
  which is used for showing participation status [1].
- Remove mistaken new line in khal implementation, refer to [2].
- Make additions to the existing test case to check the new addresses
  feature. And remove the empty lines in expected configs.

[1]: https://khal.readthedocs.io/en/latest/configure.html#the-calendars-section
[2]: https://github.com/nix-community/home-manager/pull/5192#pullrequestreview-1975091763

modules/programs/khal-accounts.nix

@@ -31,5 +31,14 @@ with lib;
         Priority of a calendar used for coloring (calendar with highest priority is preferred).
       '';
     };
+
+    addresses = mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      description = ''
+        Email addresses to be associated with this account. Used to check the
+        participation status ("PARTSTAT"), refer to khal documentation.
+      '';
+    };
   };
 }

modules/programs/khal.nix

@@ -45,8 +45,10 @@ let
         + (optionalString
           (value.khal.type == "birthdays" && value.khal ? thisCollection)
           value.khal.thisCollection)
-      }\n        "
+      }"
     ] ++ optional (value.khal.readOnly) "readonly = True"
+      ++ optional (value.khal.addresses != [ ])
+      "addresses= ${lib.concatStringsSep ", " value.khal.addresses}"
       ++ optional (value.khal.color != null) "color = '${value.khal.color}'"
       ++ [ (toKeyValueIfDefined (getAttrs [ "type" "priority" ] value.khal)) ]
       ++ [ "\n" ]);