make notmuch search.exclude_tags configurable

modules/programs/notmuch.nix

@@ -46,7 +46,7 @@ let
           };
 
         search = {
-          exclude_tags = [ "deleted" "spam" ];
+          exclude_tags = cfg.search.excludeTags;
         };
       }
       cfg.extraConfig;
@@ -138,6 +138,19 @@ in
           '';
         };
       };
+
+      search = {
+        excludeTags = mkOption {
+          type = types.listOf types.str;
+          default = [ "deleted" "spam" ];
+          example = [ "trash" "spam" ];
+          description = ''
+            A  list  of  tags  that  will be excluded from search results by
+            default. Using an excluded tag in a  query  will  override  that
+            exclusion.
+          '';
+        };
+      };
     };
   };