REGEX-Escape for: users[@.id=='{appUserId}']

Your Input:
Result, the escaped string:
users\[@\.id\=\='\{appUserId\}'\]

What must the escaping look like for:
users[@.id=='{appUserId}']

The excaped text for use in a regex is:
users\[@\.id\=\='\{appUserId\}'\]