create ResponseMapStringString class to be used in @Schema to define …

…HashMap<String, String>

services/src/main/java/org/fao/geonet/api/tools/i18n/TranslationApi.java

@@ -273,12 +273,30 @@ public void deleteTranslations(
     }
 
 
+    // Class used by getDbTranslations to define schema being returned.
+    // Based on https://github.com/swagger-api/swagger-core/issues/3724#issuecomment-718761089
+    private class ResponseMapStringString extends HashMap<String, String>
+    {
+        private static final long serialVersionUID = 6453256719377446479L;
+    }
+
     @io.swagger.v3.oas.annotations.Operation(
         summary = "List database translations (used to overrides client application translations).")
     @GetMapping(value = "/db/translations",
         produces = {
             MediaType.APPLICATION_JSON_VALUE
         })
+    @ApiResponse(
+        responseCode = "200",
+        content = @Content(mediaType = "application/json", examples = {
+            @ExampleObject(value =
+                "{" +
+                    "  \"translationKey1\": \"Translated Key One\",\n" +
+                    "  \"translationKey2\": \"Translated Key Two\",\n" +
+                    "  \"translationKey3\": \"Translated Key Tree\"\n" +
+                    "}")
+        }, schema = @Schema(implementation = ResponseMapStringString.class))
+    )
     @ResponseStatus(OK)
     @ResponseBody
     public Map<String, String> getDbTranslations(