trigger re-index and optimize query by social field

[call-me-matt]

trigger re-index of contacts to optimize query in background updates

[call-me-matt]

This is a follow-up of nextcloud/server#22085
This code is untested, I would be interested in feedback before continuing.

[codecov]

Codecov Report

Merging #1744 into master will decrease coverage by 2.11%.
The diff coverage is 4.54%.

@@             Coverage Diff              @@
##             master    #1744      +/-   ##
============================================
- Coverage     40.05%   37.93%   -2.12%     
- Complexity      128      133       +5     
============================================
  Files            17       18       +1     
  Lines           377      398      +21     
============================================
  Hits            151      151              
- Misses          226      247      +21     

Impacted Files	Coverage Δ	Complexity Δ
lib/Migration/BuildSocialSearchIndex.php	0.00% <0.00%> (ø)	5.00 <5.00> (?)
lib/Service/SocialApiService.php	88.42% <100.00%> (ø)	36.00 <0.00> (ø)

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[nickvergessen]

It's a repair step, exactly what it should be, but it's not registered in info.xml

[georgehrke]

BuildSocialSearchIndex should not be part of the Contacts app, but in dav in the server.
Apps should not use classes from other apps or access their database tables.

Futhermore, the actual indexing shouldn't be done in the migration step, but the migration step should only register a background job that will re-index them in smaller chunks. There are Nextcloud instances storing millions and millions of contacts, a simple repair-step would timeout here or block the update for hours.

See https://github.com/nextcloud/server/blob/master/apps/dav/lib/Migration/BuildCalendarSearchIndex.php
It's only fetching the biggest id from the database and registering a re-index job, which later reindexes all events with an id lower than the one from the repair step.

Also see https://github.com/nextcloud/server/blob/master/apps/dav/lib/Migration/BuildCalendarSearchIndexBackgroundJob.php#L79L87 and https://github.com/nextcloud/server/blob/master/apps/dav/lib/Migration/BuildCalendarSearchIndexBackgroundJob.php#L116L118.

The background-job does not re-index everything at once, but only 15 seconds per background-job and continues where it left of previously.

[call-me-matt]

Thank you for your feedback, I will move the code to the server then (and pack it into background-chunks)