Currently the progress sent to the server can be either a string or an int (depending on whetther the document has pages).
The following are both payload sent from koreader to the server.
```
{"percentage":0.005,"device":"device_name","device_id":"B78EA04ACC3A453DBA220D720C0BE102","document":"348e34463a44ba68659fc6fe814a6778","progress":3}
```
where document `348e34463a44ba68659fc6fe814a6778` is a pdf file.
```
{"percentage":1,"device":"device_name","device_id":"B78EA04ACC3A453DBA220D720C0BE102","document":"4eb484b229696cb39cd8fe5495aa1bbe","progress":"\/body\/DocFragment[30]\/body\/p\/img.0"}
```
where document `4eb484b229696cb39cd8fe5495aa1bbe` is an epub file.
This may add extra work to the backend server. A few commits were added to my personal fork of [kosyncsrv](https://github.com/yeeac/kosyncsrv) (a kosync backend server). kosyncsrv initially tries to decode progress as a string. It then failed on document with pages (in which, progress is just integer page number). I then change the field's type, only to [revert it later](8a642e31a0).
I believe it is more appropriate for us to fix the progress type to string.
This reverts commit d90e221a17. Reverts #6489 since it introduced problems for people having [*]Auto sync now and in the furture & Action when wifi off: prompt.
The 'KOSync' plugin will synchronize furthest reading progress
across different koreader devices after users registering their
devices.
The synchronizing service is open-sourced as the project
[koreader/koreader-sync-server](https://github.com/koreader/koreader-sync-server).
