change severities for some rules to enforce our way of working

.spectral.yml

@@ -3,3 +3,9 @@ extends:
   #  - https://italia.github.io/api-oas-checker/spectral.yml
   - https://italia.github.io/api-oas-checker/spectral-generic.yml
   - https://italia.github.io/api-oas-checker/spectral-security.yml
+rules:
+  no-default-additionalProperties: hint
+  string-maxlength: hint
+  typed-enum: error
+  paths-status: warn
+  response-with-json-object: error