Support both "example" and "examples" in the request body

[derevnjuk]

Description

We are currently unable to extract the request body from "examples". When attempting to fill in the value, the error message The property `application~1x-www-form-urlencoded` must have either `example` or `examples`, but not both, as they are mutually exclusive is displayed due to the "example" parameter being added when the request already has "examples".

Steps to reproduce

To reproduce the issue, follow these steps:

1. Parse the my-oas.json file (see below) using the following code:

import { OasV3Editor } from '@har-sdk/editor';
import { readFile } from 'node:fs/promises';

const  openApiParser = new OasV3Editor();

await openApiParser.setup(
  await readFile(
    './my-oas.json',
    'utf-8'
  )
);

const result = openApiParser.parse();

2. Ensure that the parameters of the /paths/~1api~1users/post tree node contain the appropriate values:

{
  "bodyType": "application/x-www-form-urlencoded",
  "paramType": "requestBody",
  "value": {
    "email": "bob@example.com",
    "password": "Qwerty1"
  },
  "valueJsonPointer": "/paths/~1api~1users/post/requestBody/content/application~1x-www-form-urlencoded/~1examples~1example-1~1value"
}

my-oas.json

{
  "openapi": "3.0.0",
  "info": {
    "title": "Support both `example` and `examples` in the request bodies",
    "description": "Ensure accurate extraction of the request body example.",
    "version": "1.0",
    "contact": {}
  },
  "tags": [],
  "servers": [
    {
      "url": "https://brokencrystals.com"
    }
  ],
  "components": {
    "schemas": {
      "User": {
        "type": "object",
        "properties": {
          "email": {
            "type": "string",
            "format": "email"
          },
          "password": {
            "type": "string",
            "format": "password"
          }
        },
        "required": ["email", "password"]
      }
    }
  },
  "paths": {
    "/api/users": {
      "post": {
        "description": "Should use value from `content[mime].examples`",
        "parameters": [],
        "requestBody": {
          "required": true,
          "content": {
            "application/x-www-form-urlencoded": {
              "schema": {
                "$ref": "#/components/schemas/User"
              },
              "examples": {
                "example-1": {
                  "value": {
                    "email": "bob@example.com",
                    "password": "Qwerty1"
                  }
                }
              }
            }
          },
          "description": ""
        },
        "responses": {
          "200": {
            "description": "OK",
            "content": {}
          }
        }
      }
    }
  }
}

Actual result

The parsing is completed without errors, however, the resulting node is missing the expected value and contains an unexpected valueJsonPointer.

Expected result

The request body value should first be filled from the "examples", followed by "example". If both of them are absent, the "example" from the "schema" can be used as a last resort.