I should be able to check whether a substring is contained within a String

(User Story, Closed -> Fixed, Priority: Critical, Test Status: Unit tested , Reported By Bad Link: Thing 3y284oe not found, )
Summary:
From Eric:
Is there any function that does what I would expect _containsSubstring or _stringPosition to do - test whether a received Text/Long Text has a particular substring?

The only thing I'm seeing is _search, but that's very broad-powered; I was just looking for something to use in a fairly straightforward _filter.
This seems totally reasonable and easy. Probably best solved initially with a _textPositions function that returns a List of all of the positions of the desired substring; that can then be tested for _isEmpty easily.