Unquoted integer `example:` value fails to parse when the spec includes a deeply nested schema elsewhere in spec

Version: 2.1.29

Description:
We are seeing issue parsing a valid OpenAPI 3.0 spec with an unquoted example: when the spec includes a deeply nested schema elsewhere.

Steps to Reproduce:
When we try and parse this spec we don't see the error directly:

openapi: 3.0.1
info:
  title: "Infinity reproduction"
  version: 1.0.0
servers:
  - url: http://example.com
paths:
  /some-endpoint:
    get:
      responses:
        "200":
          description: Get something from endpoint 
          content:
            application/json:
              schema:
                type: string
                example: 68534049e7548

Internally this seems to be converted into json in the following way:

{
  "openapi" : "3.0.1",
  "info" : {
    "title" : "Infinity reproduction",
    "version" : "1.0.0"
  },
  "servers" : [ {
    "url" : "http://example.com"
  } ],
  "paths" : {
    "/some-endpoint" : {
      "get" : {
        "responses" : {
          "200" : {
            "description" : "Get something from endpoint",
            "content" : {
              "application/json" : {
                "schema" : {
                  "type" : "string",
                  "example" : "Infinity"
                }
              }
            }
          }
        }
      }
    }
  }
}

See the value 68534049e7548 has been converted into Infinity. In our system this is not an issue for parsing although not ideal given it doesn't represent the example in the original yaml specification.

However, if I try to parse this document with a deply nested respose in s different path:

openapi: 3.0.1
info:
  title: "Number format bug reproduction"
  version: 1.0.0
servers:
  - url: http://example.com
# this should fail and throw a number format exception in OpenAPIDeserializer.java caught on line 315
paths:
  /foo:
    get:
      responses:
        "200":
          description: Get something
          content:
            application/json:
              schema:
                type: string
                example: 68534049e7548
  /bar:
    get:
      responses:
        "200":
          description: Get something else
          content:
            application/json:
              schema:
                type: object
                properties:
                  flows:
                    type: array
                    items:
                      type: object
                      properties:
                        frames:
                          type: array
                          items:
                            type: object
                            properties:
                              root:
                                type: object
                                properties:
                                  children:
                                    type: array
                                    items:
                                      type: object
                                      properties:
                                        children:
                                          type: array
                                          items:
                                            type: object
                                            properties:
                                              children:
                                                type: array
                                                items:
                                                  type: object
                                                  properties:
                                                    children:
                                                      type: array
                                                      items:
                                                        type: object
                                                        properties:
                                                          children:
                                                            type: array
                                                            items:
                                                              type: object
                                                              properties:
                                                                children:
                                                                  type: array
                                                                  items:
                                                                    type: object
                                                                    properties:
                                                                      children:
                                                                        type: array
                                                                        items:
                                                                          type: object
                                                                          properties:
                                                                            children:
                                                                              type: array
                                                                              items:
                                                                                type: object
                                                                                properties:
                                                                                  children:
                                                                                    type: array
                                                                                    items:
                                                                                      type: object
                                                                                      properties:
                                                                                        children:
                                                                                          type: array
                                                                                          items:
                                                                                            type: object
                                                                                            properties:
                                                                                              children:
                                                                                                type: array
                                                                                                items:
                                                                                                  type: object
                                                                                                  properties:
                                                                                                    id:
                                                                                                      type: string

What seems to be happening is the the 68534049e7548 value has been converted into Infinity and then it tries to parse it as a BigDecimal which failes with a java.lang.NumberFormatException: Character I is neither a decimal digit number, decimal point, nor "e" notation exponential mark.

The simple workaround is to quote the 68534049e7548 value and then it is treated as a string. The problem with that is the quotes are often removed when the spec is output and saved after parsing. We then have the same probem when the spec is parsed the next them round.

Start with OpenAPIDeserializer.java, especially the parsing path around the line 315 catch mentioned in the report. Reproduce the minimal and deeply nested OpenAPI documents, comparing how the unquoted example value is converted. Done means the valid value is preserved without converting to Infinity or raising a BigDecimal NumberFormatException.