victoriametrics & vmagent: Make the config check optional

This follows the pattern that AlertManager uses. Currently if you use
environment variables, the config check will fail.

nixos/modules/services/databases/victoriametrics.nix

@@ -24,10 +24,13 @@ let
 
   checkedConfig =
     file:
-    pkgs.runCommand "checked-config" { nativeBuildInputs = [ cfg.package ]; } ''
-      ln -s ${file} $out
-      ${lib.escapeShellArgs startCLIList} -promscrape.config=${file} -dryRun
-    '';
+    if cfg.checkConfig then
+      pkgs.runCommand "checked-config" { nativeBuildInputs = [ cfg.package ]; } ''
+        ln -s ${file} $out
+        ${lib.escapeShellArgs startCLIList} -promscrape.config=${file} -dryRun
+      ''
+    else
+      file;
 in
 {
   options.services.victoriametrics = {
@@ -127,6 +130,17 @@ in
         or {command}`victoriametrics -help` for more information.
       '';
     };
+
+    checkConfig = lib.mkOption {
+      type = lib.types.bool;
+      default = true;
+      description = ''
+        Check configuration.
+
+        If you use credentials stored in external files (`environmentFile`, etc),
+        they will not be visible  and it will report errors, despite a correct configuration.
+      '';
+    };
   };
 
   config = lib.mkIf cfg.enable {

nixos/modules/services/monitoring/vmagent.nix

@@ -30,10 +30,13 @@ let
 
   checkedConfig =
     file:
-    pkgs.runCommand "checked-config" { nativeBuildInputs = [ cfg.package ]; } ''
-      ln -s ${file} $out
-      ${lib.escapeShellArgs startCLIList} -promscrape.config=${file} -dryRun
-    '';
+    if cfg.checkConfig then
+      pkgs.runCommand "checked-config" { nativeBuildInputs = [ cfg.package ]; } ''
+        ln -s ${file} $out
+        ${lib.escapeShellArgs startCLIList} -promscrape.config=${file} -dryRun
+      ''
+    else
+      file;
 in
 {
   imports = [
@@ -119,6 +122,17 @@ in
         or {command}`vmagent -help` for more information.
       '';
     };
+
+    checkConfig = lib.mkOption {
+      type = lib.types.bool;
+      default = true;
+      description = ''
+        Check configuration.
+
+        If you use credentials stored in external files (`environmentFile`, etc),
+        they will not be visible  and it will report errors, despite a correct configuration.
+      '';
+    };
   };
 
   config = lib.mkIf cfg.enable {