Remove some shadowed mappings, improve error message

Models/ThemeConfig/Conversion/Validation.ts

@@ -276,7 +276,13 @@ export class DetectShadowedMappings extends DesugaringStep<TagRenderingConfigJso
     The mapping ${parsedConditions[i].asHumanString(false, false, {})} is fully matched by a previous mapping (namely ${j}), which matches:
     ${parsedConditions[j].asHumanString(false, false, {})}.
     
-    Move the mapping up to fix this problem
+    To fix this problem, you can try to:
+    - Move the shadowed mapping up
+    - Use "addExtraTags": ["key=value", ...] in order to avoid a different rendering
+         (e.g. [{"if": "fee=no",                     "then": "Free to use", "hideInAnswer":true},
+                {"if": {"and":["fee=no","charge="]}, "then": "Free to use"}]
+          can be replaced by
+               [{"if":"fee=no", "then": "Free to use", "addExtraTags": ["charge="]}]
 `)
                 }
             }

assets/themes/buurtnatuur/buurtnatuur.json

@@ -538,16 +538,7 @@
               ]
             },
             "then": "Beheer door een privépersoon",
-            "hideInAnswer": true
-          },
-          {
-            "if": {
-              "and": [
-                "operator:type=private",
-                "operator="
-              ]
-            },
-            "then": "Beheer door een privépersoon"
+            "addExtraTags": ["operator="]
           }
         ],
         "condition": {

assets/themes/campersite/campersite.json

@@ -199,12 +199,8 @@
                 "nl": "Kan gratis gebruikt worden",
                 "pt_BR": "Pode ser usado de graça",
                 "de": "Nutzung kostenlos"
-              }
-            },
-            {
-              "if": "fee=no",
-              "then": "Can be used for free",
-              "hideInAnswer": true
+              },
+              "addExtraTags": ["charge="]
             }
           ]
         },