userId match type should allow =@

[LauraHornbake]

Currently userId match type is restricted to ==, ::NOT_NULL, ::NULL, !=. This creates the following problem:

I am working on creating segments for users on an intranet and have used the users' emails set as userId. I want to create a segment that matches the domain end of that email/userId. for example:

With userIds like this:
[email protected]
[email protected]

I want to have segments like this:
"Department 1" segment: userId =@ department1.com
"Department 2" segment: userId =@ department2.com

but I cannot, I get the error:

[mattab]

Thanks for suggestion. After #6954 we can revert this commit: 252798d (removing the system test also)