Eliminate Kernel::System::FileTemp

[bschmalhofer]

I see no benefits of this module over using File::Temp directly. It does set up a non-standard location for temporary dirs. But I don't think that this is a benefit.

[svenoe]

I don't know every way otobo is set up on systems. If someone wants to give minimal access to the otobo-user, or just have all otobo-files in one place for a better overview, or maybe disk space limitations, it's not a bad thing to be able to, in my opinion.

[bschmalhofer]

Reading the documentation of File::Temp I find that this is trickier than expected, and I agree that keeping Kernel::System::FileTemp might be useful.
However, looking at the code in Kernel/Modules/AgentTicketAttachment.pm, I still find that the object oriented interface of File::Temp would be the better approach. My impression is that Kernel::System::FileTemp first makes an effort to make the created file handle persistent, and then makes an effort to clean up after the end of the current request. File::Temp::new() does kind of the same thing, but makes it easy to limit the life time of the temporary file to a small scope.

Thomas Fahle tells it like it is in https://perl-howto.github.io/2008/07/temporare-dateien-sicher-erzeugen.html:

File::Temp ist seit Perl 5.6.1 ein Standardmodul, d.h. es wird mit Perl ausgeliefert und läuft auf jeder Plattform, die von Perl unterstützt wird.

Dokumentation und API werden selbst von sehr gutmütigen Menschen bestenfalls als verwirrend bezeichnet.

So I propose to keep this issue open, until we find the best solution.

[bschmalhofer]

There was an inconstent usage of the file handle returned from Kernel::System::FileTemp::TempFile(). The applied PR aligns the usage in Kernel/Modules/AgentTicketAttachments.pm with the saner usage Kernel/System/Crypt/PGP.pm, A test with the formatter wc -l gave the expected result.