An error should appear immediately after uploading a file of wrong extension within the size limit

Issue

• When trying to upload a file in blogs that is less than the specified limit with the wrong extension, it shows the progress bar for a while and then gives the error.
• Based on user experience, the error should appear immediately.
  
  Steps to reproduce:
  1. Navigate to System Settings --> Blogs --> File Uploads
  2. Change the Maximum Blogs Image Size to 50 MB (52428800)
  3. Navigate to Content & Data --> Blogs and create a new blog
  4. Drag and drop a file of wrong extension having size 40-49 MB. i.e. a large file but under the specified limit.
  
  Observed Behavior: Error is shown after showing a progress bar for a few moments depending on file size.
  Expected Behavior: Error message should appear immediately.

Environment

• Liferay DXP [all versions]

Resolution

1. As per the expected behavior of the product, the extension check is performed at the backend, therefore it has to be uploaded before checking it.
2. Moreover, the other checks are performed on the front side for example: size validation.