Collecting breaking changes for migration guide

[ScharfViktor]

#10373 (comment)

1. to make activity work we need add activitylog: service_account: to .ocis/config/ocis.yaml file

• run ocis binary on stable-5.0
• rebuild ocis on 6.1.1 version (Result: activities don't work)
• run ocis/bin/ocis init --diff
• a new activitylog service entry containing service_account: data has been added
  this is because the activitylog service has been added. it will not be active without this setting.
  note that the diff also highlights other, non breaking but necessary changes.
• put suggested activitylog: block to ocis.yaml and run ocis again (1)
  note that activity now works, any activities before this fix will not get handled and are lost.

(1) ... the ocis init --diff command creates a patch file named ocis.config.patch and a backup file. Most easiest is to apply the path file with: patch < ocis.config.patch from the directory of the config file.

cc @mmattel

[ScharfViktor]

we need a fully change this page https://doc.owncloud.com/ocis/next/deployment/wopi/wopi.html#wopi-configuration-examples because we don't use cs3org/wopiserver anymore

[ScharfViktor]

need to add COLLABORATION_WOPI_SECRET: "some-wopi-secret-onlyoffice"toonlyoffice.yml->collaboration-oo->enviromentor/andcollabora.yml->collaboration->enviroment`

more detais here: #10373 (comment)

[mmattel]

need to add COLLABORATION_WOPI_SECRET: "some-wopi-secret-onlyoffice"toonlyoffice.yml

We have a bug in the ocis init --diff command. The command DOES add a secret, but the secret value is empty. A secret value MUST be added, see issue: #10560