Looking up key event directly using dgkey (pre, dig) from db.evts instead of db.fons under the assumption that the event was first seen (accepted)

[SmithSamuelM]

Feature request description/rationale

Events in .evts may be in escrow or may be duplicitous etc. In other words they are not guaranteed to have been validated and accepted as first seen.

Valid first seen events are indexed by sn in db.kels using snkey (pre, sn) or by fn in db.fels using fnkey (pre,fn) or in db.fons (dgkey (pre, dig). To find an event by its dgkey (pre,dig) that has been first seen one may use db.fons which indexes first seen events in .fels by their dgkey (pre, dig).

So lookup fn in db.fons given dgkey then lookup event in db.evts by dgkey since already have dgkey.
Task is to find places in code when the false assumption is being made that an event in .evts has been first seen without checking that the event is in .fels or .kels or .fons