postJson method
Implementation
Future<Response> postJson(String path, Map<String, dynamic> body, {String? contentType, Map<String, String>? headers}) async {
if (path.startsWith("/")) {
path = path.substring(1);
}
final url = baseUrl.resolve(path);
final bodyText = jsonEncode(body);
return httpClient.post(url,
headers: getHeaders({"content-type": contentType ?? "application/json", if (headers != null) ...headers}), body: bodyText);
}