PropertyResolverUtils.resolveExtensions converts ObjectNode instances to strings

[marr1977]

Describe the bug

PropertyResolverUtils.resolveExtensions will convert ObjectNode instances to Strings in cases where the extension value is a HashMap

If value1, i.e. the hashmap value, is an ObjectNode, it will be converted to a String by the line below:

String value1Resolved = this.resolve(value1.toString(), locale);

A possible solution is to only call "resolve" if "value1 instanceof String", as is done for non-hashmap extension values.

To Reproduce

• What modules and versions of springdoc-openapi are you using? 3.0.1

We have extension properties as part/children of extension-values where the extension property is a json-object, example below:

  @Extension(
                                 name = "x-my-extension",
                                 properties = {
                         		   @ExtensionProperty(
                                                  name = "working-hours",
                                                  parseValue = true,
                                                  value = "{  \"working-hours\": \"Weekdays 00:15 - 22:59 CET\" }"
                                         ),

The output of this is the following

"x-my-extension": {
  "working-hours": "{\"working-hours\":\"Weekdays 00:15 - 22:59 CET\"}",

I.e. the value is a string and not a JSON object.

Expected behavior

I expect the result to be a JSON object, like below:

"x-my-extension": {
  "working-hours": { "working-hours": "Weekdays 00:15 - 22:59 CET" },

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