If a field name into the parser definition doesn't exist into the model but is resolved by a callable, call the method. Prior to this change, it was o more possible to define computed json value for custome keys

Quite handy to take full control of the final result.

Orig commit msg:

[ADD] use jsonifier features to retund postprocessed values, containing
field string as well

Better Version, not using function features , leaves parser syntax
intact.

[FIX] Review fixes

[FIX] small comment and style fix

An invalid field must be skipped in any case if not in strict mode.
Error message has been downgraded to warning since is not really broken
till you use string mode.

Log tests reworked.

The resolver was returned as a full recordset,
hence its cursor could diverge from the original one
and get closed while the other was still active.