SyncStatus docs

[MontrealSergiy]

SyncStatus' status_transition method docs say

This method changes the status attribute in the current task object

should be sync_status status instead? Is so, correct to reduce confusion?

also, docs says lock ensures collision of two status updates, which is not 100% accurate. MySql is arguably 'lightweight' db

mysql Innodb lock reduces chances of issues, but does 100% guaranty absence of phantom writes (duplicating sync objects), so as you done recently db uniqueness constraints are typically used

[prioux]

Documentation adjusted, will go into a future commit.