Bump ical2j from 1.0.5 to a recent version and fix ICal4JWrapperTest

[ursjoss]

We currently use net.fortuna.ical4j-1.0.5 which is from 2013.

We should use one of the lastest of org.mnode.ical4j-4.x instead.

Also, there seems to be an off-by-one issue with that version, as can be seen in the ICal4JWrapperTest. We should check if upating to a more recent version fixes that bug.

[ursjoss]

New information coming out of #51: While the test was fixed in #27 to succeed on my laptop, it failed on github actions. I reverted the expected value to the original one in #51, expecting it to pass on CI (Github Actions) but fail on my machine for now.

I suspect that this flaky behavior is related to different time-zone settings. Options we have - after upgrading ical4j, potentially profitting from bug fixes on their side:

• control the environment through test-setup (that should be done anyhow)
• potentially and if necessary: setting the time-zone on Github Actions
• ???

[ursjoss]

Update: The flaky test is completely ignored for now (in #51 ).