Added AJAX validation for folders in File manager; #3818

[Yulyaswan]

Added validation to "New Folder" dialog in the Files area to prevent users from trying to create folders with unacceptable symbols in a file name
Resolved #3818

[intoeetive]

@Yulyaswan can you resolve conflict here as well?

[intoeetive]

Please see the comments in code.

Also, this seems to be very specific (used only on Files controller) and yet included into common.js

I think we need to either have it included on Files page only, or (and I think that would be better) rewrite it in the way so it could be applied to any form in modal.

[intoeetive]

@Yulyaswan sorry, I wasn't clear enough.

We don't need to call validation on every form on popup. We just need a way to be able to call it on the forms where we need that. For the time being, we only need validation for "new folder" and "rename folder" dialog. I think on channel entry form, the validation is triggered by the class class="ajax-validate", so perhaps we could do the same here

[intoeetive]

@Yulyaswan this works fine - however what I noticed is that the validation is only triggered when you blur out of the field.

This is same as with the "regular" forms, but because we have just 1 field here, this might never happen

So I wonder if we need to change the init for validation, so that of there's just one text input from _textInputSelectors it would trigger ajax not just on blur but also on like "when they make a pause in typing"

[intoeetive]

@Yulyaswan this now seems to be sending multiple requests each time I type

[intoeetive]

@Yulyaswan just a reminder on this one