Reordering of the attendees should not be a signitifcant change (#540)

[floerke]

#540

If a server (using sabre) receives a VEVENT update it will send mails to all attendees. Not for all modified events, but for events with a "significant change". The calculation of "signifcant change" is done by vobject.

I have trouble with to many "Invitation: ..."-Mails for events that has not been changed.

Investigating this I have seen:

• the events were modified by the client and sent to the server (eg. to save the acknowledgment of an alarm).
• the client has changed the order (not the attendees itself) of the attendees in the modified event
• vobject calculated a "significant change"
• the server sent the email

I think everything is correct, except, the reordering is not a significant change. Why the client desires to reorder the attendees? I don't know, but I think this should not be a significant change.

[staabm]

Sounds reasonable. Could you add a unit test?

[floerke]

Hi Markus, I added a new unittest...

[phil-davis]

Rebased and squashed to get fresh CI. LGTM.

[codecov]

Codecov Report

Merging #541 (5f81c0f) into master (6ef9328) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master     #541   +/-   ##
=========================================
  Coverage     98.69%   98.69%           
- Complexity     1816     1817    +1     
=========================================
  Files            66       66           
  Lines          4445     4448    +3     
=========================================
+ Hits           4387     4390    +3     
  Misses           58       58           

Impacted Files	Coverage Δ
lib/ITip/Broker.php	99.51% <100.00%> (+<0.01%)	⬆️

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