feat(fields): trim string variables before use [CLK-547306]

[mysza]

Summary

As string variables can be used in comparisons, we must ensure that whitespace before or after the variable value does not distort the comparison result.
For example, long_text custom field always adds \n character at the end of the string, which causes issues when comparing the variable with some known string.

Testing

• all existing tests ✅
• added specific test for this fix