In the Media type configuration page, webhook parameter fields are 2048 characters long.

However, in the Test dialog they are 255 characters long. Pasting an URL - for example a teams_endpoint - can lead to an incomplete URL, which might not be noticed by the user.

Steps to reproduce:

1. Clic Test on a webhook Media Type 
2. Paste or type a long string in a parameter field

Result:
The field is truncated to 255 characters.
Expected:
The field should allow 2048 characters, as it does in the Media type configuration page.