[9.x] Add zero-width space to trimmed characters in TrimStrings middleware

[tomcodes]

I had a weird bug recently when adding a job to the queue when the content had a zero-width space present somewhere.

The bug I had was: Unable to JSON encode payload. Error code: 5

It took me a while to corner this issue to a zero-width space present in a user firstname.

I was wondering also if would be interesting to add a middleware to actually remove those characters also from within the fields instead of just the side. I am willing to create another pull request if that need can benefit more people.

Github does not show the diff, so here is a visual diff:

Before

After

[tomcodes]

Also, I can try and add a test for this if necessary.

[taylorotwell]

Yeah we would definitely want a test for this I think.

[taylorotwell]

Please mark as ready for review when it has a test.

[tomcodes]

I tried to think of multiple situations with the tests, I hope it's fine like this!

[tomcodes]

woops, I have noticed a tiny typo issue in the last test, should I open a new pull request?

The title should not be This title contains a zero-width non-breakable space at the end, it should be This title contains a combination of zero-width non-breakable space and zero-widh spaces characters at the begining and the end instead.

The test is still valid, it's just the title that does not fit the test name.

[driesvints]

@tomcodes yes feel free to send in a new pr