prometheus: add tls_config

nixos/modules/services/monitoring/prometheus/default.nix

@@ -237,6 +237,14 @@ let
           Optional http login credentials for metrics scraping.
         '';
       };
+      tls_config = mkOption {
+        type = types.nullOr promTypes.tls_config;
+        default = null;
+        apply = x: mapNullable _filter x;
+        description = ''
+          Configures the scrape request's TLS settings.
+        '';
+      };
       dns_sd_configs = mkOption {
         type = types.listOf promTypes.dns_sd_config;
         default = [];
@@ -431,6 +439,48 @@ let
     };
   };
 
+  promTypes.tls_config = types.submodule {
+    options = {
+      ca_file = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = ''
+          CA certificate to validate API server certificate with.
+        '';
+      };
+      cert_file = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = ''
+          Certificate file for client cert authentication to the server.
+        '';
+      };
+      key_file = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = ''
+          Key file for client cert authentication to the server.
+        '';
+      };
+      server_name = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = ''
+          ServerName extension to indicate the name of the server.
+          http://tools.ietf.org/html/rfc4366#section-3.1
+        '';
+      };
+      insecure_skip_verify = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Disable validation of the server certificate.
+        '';
+      };
+    };
+  };
+
+ 
 in {
   options = {
     services.prometheus = {