Document: Add background:execute occ command for running cron jobs manually

[mmattel]

References: owncloud/core#31617 (Add background:execute occ command for running cron jobs manually)

@butonic

[mmattel]

Core issue open: owncloud/core#31727 (Harmonize printout: background:queue/execute commands)

https://github.com/owncloud/documentation/issues/4180 (Document: Add background:execute occ command for running cron jobs manually)

[voroyam]

@mmattel is everything merged or is work to be done?

[mmattel]

Master has not been merged
and stable10 not been created (that is the reason for label: waiting for PR merge)
Things are a bit tricky, because for stable10 it is intended to have some PR´s to be added to one...
See issue comment from @DeepDiver1975 (different but related PR) owncloud/core#31630 (comment)

But what can be done in the meanwhile is, to prepare the text...

[mmattel]

NOTE: this will be 10.2 only, no backporting, label is set !

@phil-davis @PVince81 @jvillafanez
Pls help with text suggestions

[phil-davis]

In stable10 the background commands are now:

 background
  background:ajax                     Use ajax to run background jobs.
  background:cron                     Use cron to run background jobs.
  background:queue:delete             Delete a job from the queue
  background:queue:execute            Run a single background job from the queue
  background:queue:status             List queue status
  background:webcron                  Use webcron to run background jobs.

In modules/admin_manual/pages/configuration/server/occ_command.adoc I can see words about ajax, cron, webcron. But nothing yet about background:queue:*

All 3 background:queue commands have been recently added to core stable10. So doc needs to be added to cover all 3.

[mmattel]

For ease of implementation, see following link, this just needs some copy / paste and adoption to .adoc 😄 https://github.com/owncloud/documentation/pull/4207/files#diff-0380163502e27936a0c96cf3eb64fe58R269