Add a second line of defense for critical unwanted behavior

[zukunft]

To prevent issues like #13872 a suggestion is to add a second line of defense for critical unwanted behavior. The suggested limits are:

• max CPU usage within an hour e.g. 10%. If the app requests more, get a confirmation from the user with a question like "Nextcloud has used the x% CPU capacity of your phone to sync x files and transferred x MB/GB within the last hour. If you want to continue, you can set the warning limit to 25%, 50%, 75% or 100% of the CPU usage (or only for the next x hours). If you do not change the limit, the synchronization might be delayed".

• max daily net traffic via "a know wifi" (local/home/...), other wifi or mobile data of 1 GB or 20% percent of server data size. If the limit is exceeded the question to the user could be: "Nextcloud has synced x files and transferred x MB/GB within the last 24 hours with the xxx wifi/mobile data connection. If you want to continue, you can increase the warning limit to x MB/GB or x% of your server space or switch the limit off". This is related to Remote & Local Connection in one Account #13605

• max sync events per file and day to 5 times the average of the first week. If a file is synced more often the question to the user could be: "Nextcloud has synced the file xxx x times in the last week. If you want to continue, you can increase the warning limit to x times per week for the file / parent folder / parent folders / all files or switch off this warning"

[noci2012]

Additional:

• in place of potential BULK operations like sync etc. First build the brakes... (Allow/DisAllow option X, before actual providing option X..., then at least someone can hit the brakes before crashing & burning .....
  If option X doesn't turn out to work as intended/advertised at least there is a way to limit it.

[jens-br]

Additional:

• max local storage usage

E.g. phones with limited storage capacity can get bloated really quick over night, if such an issue happens and a big Nextcloud library is synced to the phone.