Description of problem:
First, if I enter an incorrect value, I get an alert which doesn't say anything about the pattern the value must match. So I need to open the DSL configuration and look up the pattern. It would be very helpful if the pattern was displayed in-place. The best would be an indicator next to the field, updating it's state as you type (similar to password strength indicator used when changing password of some online account).

Second, after the unsuccessful pattern-match check, the last change to the field value is discarded. This can be annoying. Imagine there's a regex-constrained input for phone number: you type a long number and if you make a mistake, the whole value is lost and you have to retype it completely.

Version-Release number of selected component (if applicable):
BRMS 5.3.0.*

How reproducible:


Steps to Reproduce:
1. import mortgage sample repository
2. open any rule and add the "When the ages is less than {num}" sentence
3. experiment with the input for "num" parameter
  
Actual results:


Expected results:
If the value does not match,
- the regex pattern should be displayed
- no changes should be made to the input

Additional info: