TF-2667 Show sending message dialog when click send button

core/lib/data/constants/constant.dart

@@ -2,6 +2,7 @@ class Constant {
   static const acceptHeaderDefault = 'application/json';
   static const contentTypeHeaderDefault = 'application/json';
   static const pdfMimeType = 'application/pdf';
+  static const base64Charset = 'base64';
   static const textHtmlMimeType = 'text/html';
   static const octetStreamMimeType = 'application/octet-stream';
   static const pdfExtension = '.pdf';

core/lib/utils/application_manager.dart

@@ -34,6 +34,7 @@ class ApplicationManager {
         userAgent = FkUserAgent.userAgent ?? '';
         FkUserAgent.release();
       }
+      log('ApplicationManager::getUserAgent: $userAgent');
       return userAgent;
     } catch(e) {
       logError('ApplicationManager::getUserAgent: Exception: $e');