Bug 1450022

Thanks for a bug report. We've been talking about this on IRC some time ago. The "Free/Busy" permission is not about sharing, it's about getting free/busy information for the participants when creating/editing meetings. Outlook overuses this permission and pretends it showing events, while it shows free/busy information instead.

The "Full details" permission is also inaccurate, 'Reader' is enough to get content of another user calendar.

The current upstream development version of evolution(-ews) doesn't allow to show free/busy information for users in the calendar views. Maybe it could be possible to overuse free/busy information within evolution-ews and pretend it being real events, with some fallback text when the shared free/busy information is without those details (I do not know, say something like "$USER busy" | "$USER Out of Office", and similar).

I opened an upstream bug [1] for this. Once it's done it can be backported to RHEL, or can be tried to backport it. It depends.

[1] https://bugzilla.gnome.org/show_bug.cgi?id=782826

Upstream bug report contains a fix for this. It has some limitations, because using Free/busy to populate calendars is rather overuse of that (Free/Busy) functionality, but if people want to have it, then it's there. The upstream bug report contains more detailed information.

To have it written here as well, the Free/Busy calendar is special, both due to its nature (Free/Busy information not being intended to be shown between regular appointments), but also due to the evolution-data-server internals (the backend part). Due to these, it behaves differently than in Outlook. Users explicitly claim to have Free/Busy information shown for particular user as events in the calendar views. Specifically, to add such calendar:
a) go to the Mail view
b) right-click the EWS account node in the folder tree and pick "Subscribe
   folder of other user"
c) write specific user name, ideally let it be auto-completed, or use
   the "Choose.." button to make sure the correct user is used
d) pick "Free/Busy as Calendar" item in the predefined special values
e) confirm the values (click the OK button).

It's verified that the Free/Busy information can be read by the logged user and if not, then an error is shown. Otherwise a new calendar is added,
named "User Name - Availability".

In case the user is granted with limited Free/Busy information the received time slots are named (the event Summary is filled with) the Free/Busy state of the time slot, which is like "Free", "Busy", "Out of Office", "Tentative". In case the user is granted with extended Free/Busy information, the provided Summary and Location are set in the events.

The time range to search Free/Busy information for is set to 1 week before today and 5 weeks after today by default. It can be changed, but there is no UI part for it. More or less intentionally, it would be hard to translate for translators. It's set to this value to not make too large queries to the server. Users can change this default by editing the corresponding .source file in:
   ~/.cache/evolution/sources/<ews-account-uid>/
The one which contains "freebusy-calendar" (quotes for clarity only) is the correct file. The values to change for queried period are:
   FreebusyWeeksBefore=1
   FreebusyWeeksAfter=5
The "before" value can be between 0 and 5, while the After value can be between 1 and 54, both inclusive. Changes in the file might require restart of the evolution-calendar-factory process (stopping it would restart it automatically by GNOME Shell, if that's the desktop the user runs, otherwise it's run on demand, like when Evolution is ran).

Side note: The user can change Permissions for its main Calendar also from within Evolution, by selecting the calendar name on the left side of the Calendar view, right-clicking it and choosing "Permissions" option in the context menu. I'm only mentioning it here, to note that it's possible to change Permissions also in Evolution, without using Outlook.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2017:2066

We tested with "Free/Busy time as calendar" and that works fine... for exactly one user. 
When I try to add a second colleague's free/busy time as calendar, I get the error message "Cannot add folder, folder already exists as $user1 - Availability" where $user1 is the name of the first colleague.

Could you please help us on it.

Thanks for the update. I did think I tested with ore than one user, but I see it might be just a feeling, because testing it now I get the same error message as you do. I'm sorry for that. I'll fix it upstream first, then we'll add it to RHEL in some way. Feel free to either reopen this bug report or fill a new.

This is an upstream fix which changes it [1]. As I wrote in the corresponding upstream bug report:

  I fixed it by changing the fake folder ID, to include also the email address
  of the other user. This change invalidates previously subscribed free/busy
  calendars, which results in an error about malformed ID. Just delete that
  calendar and re-add it again, which will correct the fake folder ID.

That was a silly mistake on my side, I'm sorry for that.

I can build evolution-ews test package for you, thus you'd be able to deliver it to the customer before it gets out through the usual channels, if you want.

[1] https://git.gnome.org/browse/evolution-ews/commit/?id=1ad1e92

(In reply to Milan Crha from comment #11)
> ...I can build evolution-ews test package for you...

As I've been testing the change myself, I made a test build here:
   https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=13899170

and copied it to a public place:
   https://people.gnome.org/~mcrha/rh1450022/

where it can be downloaded for x86_64. Just install the main package with:

  $ sudo yum update ./evolution-ews-3.22.6-6.1.el7.x86_64.rpm

then restart the machine, thus the background processes from evolution-data-server  also use the fresh bits, then you can add more than one foreign Free/Busy calendar.