Add exemption for incompatible UA (Sailfish CalDAV/CardDAV client)

[znerol]

Same as #1328 but for Jolla/Sailfish CalDAV/CardDAV client. That UA identifies as exactly Mozilla/5.0.

[mention-bot]

@znerol, thanks for your PR! By analyzing the annotation information on this pull request, we identified @LukasReschke, @bartv2 and @icewind1991 to be potential reviewers

[LukasReschke]

👎, I don't think that's the right approach to go at that. Can you provide me with a traffic dump and send that to my mail address? This exception here seems rather contraproductive if we do it for every UA out there… Then I'd prefer a generic solution.

[znerol]

I agree that adding exemptions for all the weird clients in the world is not the way to go. I just followed the path in #1328. The fact that #1593 did the same maybe indicates that there is a real problem with the changes introduced in #50.

There will always be clients which treat HTTP status >= 500 as non-recoverable. Especially API consumers which have limited possibility to interact with the user. See also the detailed description of what happens on Sailfish OS in #1603.

[mase76]

Any solution for this? Still not possible to sync carddav with sailfish os. no problems with
caldav so far.

[nicozimmermann94]

+1 for KeeWeb. Workaround right now is to alter the base.php