chg: [onlyoffice] add backup to onlyoffice, relunctantly

This should not be necessary according to current documentation, but
we had dataloss due to modifications being stuck on onlyoffice side
and not sent back to nextcloud. With some tinkering, we were able to
get the document out of cache data, so, for now, the best is to save
this data in case.

Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>

onlyoffice/metadata.yml

@@ -38,3 +38,24 @@ uses:
     auto: summon
     solves:
       database: "main storage"
+
+  ## XXXvlab: this should not be necessary as official documentation
+  ## seems to explain that all data are either logs or caches. But we
+  ## had issues with onlyoffice not sending back modifications to the
+  ## filesystem. With some tweaks, we can sometimes gets the data from
+  ## application cache.  So for now, we must include this data to
+  ## backup.
+  backup:
+    constraint: recommended
+    auto: pair
+    solves:
+      backup: "Automatic regular backups of dumps"
+    default-options:
+      ## First pattern matching wins, no pattern matching includes.
+      ## include-patterns are checked first, then exclude-patterns
+      ## Patterns rules:
+      ##  - ending / for directory
+      ##  - '*' authorized
+      ##  - must start with a '/', will start from $SERVICE_DATASTORE
+      include-patterns:
+        - /var/lib/onlyoffice/