MongoDB findAndModify() with aggregation

[Benjamin Thompson]

> The best solution probably is this:
> - try to identify the target MongoDB Server version on first connection
> and store this inside mongo db instance struct
> - to change the code in the way that if mongodb is >= 4.2 update is
> handled as an array instead of a single document.

Don't forget that 4.2 supports to old style too (so a document or
array is valid).

-- 
Ben Thompson