Additional iconv transliteration tests

[motin]

This helps isolate odd iconv transliteration behavior, to make it clear when Propel2 is at fault and when failed tests stems from incorrect/unsupported locale configuration.

[marcj]

Well, guess this is not complete since there is a PHP error in the tests

[motin]

@marcj This is now complete with passing tests

[dereuromark]

This looks nice!
Can we maybe rebase against master (or merge it) so we can check if it is still green and merge it?

[Incognito]

PHP links to libiconv installed on the host, it doesn't ship specific versions (similar to how PHP uses cURL, etc...).

Beware: A lot of this behaviour is dependent on libiconv which has serious changes between 2015 and 2020. I ran into problems in 2016/2017 on PHP 7.x (but the version of php is irrelevant) because the base debian image on the host was built with one old version of libiconv and we were migrating to a new distro release which had a more modern libiconv release.

https://www.gnu.org/software/libiconv/

libiconv changelog: https://git.savannah.gnu.org/gitweb/?p=libiconv.git;a=blob_plain;f=ChangeLog;hb=refs/heads/master

Testing this could be tricky, you can't lock it down with composer afaik.

[PhilinTv]

Add later to doc:
⚠️ Iconv transliteration tests may fail if the system locale is C or if libiconv version is inconsistent. To ensure stability, use en_US.UTF-8 locale when running tests.

[PhilinTv]

Had to refactor a bit, but it finally made it, after years of waiting :)
#2053