[dev] Horde's SabreDAV 2.0.9 and PHP 7 compat

[Ralf Lang]

Hallo,

The 2.0.9 version of sabreDav bundled with Horde_Dav does not work
correctly under php 7.2 (and possibly all php 7 versions).
While a quick check against thunderbird seems to show it's working
reasonably well, a sync with davx5/davdroid will silently fail. The
server will simply never offer any entries for syncing.

The key issue is in the CalendarQueryValidator. This is the commit
fixing it:

https://github.com/sabre-io/dav/commit/c2e3f2f093c6942c5d90bfadf1a13c06465a3361

On the weekend, I will prepare a PR to upgrade that dependency at least
to 2.1, if not 3.x - depending on the number of issues I run into.
Implementing calendar sharing, delegation or collection-sync is out of
scope for now, though.


-- 
Ralf Lang
Linux Consultant / Developer
Tel.: +49-170-6381563
Mail: lang at b1-systems.de
B1 Systems GmbH
Osterfeldstraße 7 / 85088 Vohburg / http://www.b1-systems.de
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