Add ruby 3.2 to the build mix

[mathieujobin]

No description provided.

[mtasaka]

So ruby3.2 failure maybe just due to Fixnum removal and File.exists? removal on ruby3.2...

(As far as I've checked) the first uninitialized constant Apipie::Validator::IntegerValidator::Fixnum error seems to be bringing about the following so many errors: Replacing Fixnum with Integer clears out most of the errors with leaving some errors due to File.exists? removal, which can be fixed by using File.exist?.

Although Fedora does not execute all of the tests, fixing the above 2 issues makes tests pass executed with ruby3.2 on Fedora rpm:

https://koji.fedoraproject.org/koji/taskinfo?taskID=96188951

[mathieujobin]

Thanks for the hints @mtasaka

I had not dug the issues, this is very helpful. I could apply them quickly and get it to pass.