support for negative/blank search

Hi

As per this discussion, I'm creating this feedback.

I'm trying to search for users w/o a specific prefix ( a prefix ZD insert automatically when there is a new call in ZD TALK )

(note there is a space after the Caller, cause usually, it's Caller +

created_at>2022-02-01 -name:Caller 

Also, I'm not able to search for a NONE existence of an email for a user. ( again, the same user TALK is created it automatically )