This commit introduces functionality to send POST requests withan 'application/json' content type using a Selenium WebDriver.The core logic involves:1.  Serializing a Python dictionary to a JSON string.2.  Escaping single quotes in the JSON string to allow safe embedding    into a JavaScript single-quoted string literal.3.  Dynamically generating an HTML5 document with embedded JavaScript.4.  The JavaScript uses the `fetch` API to make the POST request with    the correct 'Content-Type': 'application/json' header and the    JSON payload.5.  The HTML page (and thus the script) is loaded into the WebDriver    using a data URI.6.  Status messages (success/error) are displayed in a `div` on the    generated page and also logged to the browser console.7.  The function waits for the operation to complete and returns    the status message from the page.A demonstration example using `https://httpbin.org/post` is includedto showcase the functionality, including handling of successful requests,network errors, and HTTP error responses.This approach is designed for scenarios where direct Python HTTP requestsmight be insufficient due to browser-specific behaviors or JavaScriptdependencies on target sites.

… in Selenium.

…pe` validation. Remove obsolete `request.postJSON` logic and integrate `selenium_fetch`. Update `requirements.txt` with `selenium_fetch` dependency and enhance DTOs to support `contentType` and `response` fields.