nixos/caddy: Fix default log file for http:// hostnames (#371802)

nixos/modules/services/web-servers/caddy/vhost-options.nix

···
     logFormat = mkOption {
       type = types.lines;
       default = ''
-        output file ${cfg.logDir}/access-${config.hostName}.log
+        output file ${cfg.logDir}/access-${lib.replaceStrings [ "/" " " ] [ "_" "_" ] config.hostName}.log
       '';
       defaultText = ''
         output file ''${config.services.caddy.logDir}/access-''${hostName}.log

nixos/tests/caddy.nix

···
               "http://localhost:8081" = { };
             };
           };
+          specialisation.multiple-hostnames.configuration = {
+            services.caddy.virtualHosts = {
+              "http://localhost:8080 http://localhost:8081" = { };
+            };
+          };
           specialisation.rfc42.configuration = {
             services.caddy.settings = {
               apps.http.servers.default = {
···
             services.caddy = {
               package = pkgs.caddy.withPlugins {
                 plugins = [ "github.com/caddyserver/replace-response@v0.0.0-20241211194404-3865845790a7" ];
-                hash = "sha256-zgMdtOJbmtRSfTlrrg8njr11in2C7OAXLB+34V23jek=";
+                hash = "sha256-BorJJWICgAWU7DrpDZJWifMnIYtGWldt/4S1VELwGJI=";
               };
               configFile = pkgs.writeText "Caddyfile" ''
                 {
···
         explicitConfigFile = "${nodes.webserver.system.build.toplevel}/specialisation/explicit-config-file";
         justReloadSystem = "${nodes.webserver.system.build.toplevel}/specialisation/config-reload";
         multipleConfigs = "${nodes.webserver.system.build.toplevel}/specialisation/multiple-configs";
+        multipleHostnames = "${nodes.webserver.system.build.toplevel}/specialisation/multiple-hostnames";
         rfc42Config = "${nodes.webserver.system.build.toplevel}/specialisation/rfc42";
         withPluginsConfig = "${nodes.webserver.system.build.toplevel}/specialisation/with-plugins";
       in
···
         with subtest("multiple configs are correctly merged"):
             webserver.succeed(
                 "${multipleConfigs}/bin/switch-to-configuration test >&2"
+            )
+            webserver.wait_for_open_port(8080)
+            webserver.wait_for_open_port(8081)
+
+        with subtest("a virtual host with multiple hostnames works"):
+            webserver.succeed(
+                "${multipleHostnames}/bin/switch-to-configuration test >&2"
             )
             webserver.wait_for_open_port(8080)
             webserver.wait_for_open_port(8081)