pass access token ttl value to wopi client

[karakayasemi]

Wopi protocol suggests returning access_token_ttl value to wopi client. In this way, wopi client can decide what to do when token about to expire.
For example, collabora warns user when 15 minutes before expire and shows below message to user:

If user still doesn't refresh the session, it warns again periodically in every 2 minutes.

Fixes owncloud/enterprise#4237

[mrow4a]

exactly how I would expect it to work. Great work! Unit tests not straightforward I belive?

[codecov]

Codecov Report

Merging #364 (f489f0b) into master (e302823) will increase coverage by 3.02%.
The diff coverage is 31.25%.

@@             Coverage Diff             @@
##             master    #364      +/-   ##
===========================================
+ Coverage      6.16%   9.18%   +3.02%     
  Complexity      307     307              
===========================================
  Files            14      14              
  Lines          1200    1197       -3     
===========================================
+ Hits             74     110      +36     
+ Misses         1126    1087      -39     

Impacted Files	Coverage Δ	Complexity Δ
lib/Controller/DocumentController.php	1.75% <0.00%> (-0.01%)	139.00 <0.00> (ø)
lib/Db/Wopi.php	63.88% <83.33%> (+63.88%)	5.00 <0.00> (ø)
lib/Db.php	15.66% <0.00%> (+15.66%)	33.00% <0.00%> (ø%)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e302823...f489f0b. Read the comment docs.

[karakayasemi]

There is no dependency injection in php classes. Also, touched classes have too many \OC::$server, static method usage etc. JS side has not single unit test. Yes, nearly imposible to test without big refactoring. Seems like test can be written only to newly added classes in this repository. Maybe @micbar can help to merge as it is.

[karakayasemi]

@phil-davis Could you help for merging this pull request?