Writes every journalled key to the store, sealed; deletes what is gone.
One flush at a time per process: a call made while one is in flight waits
for it and then takes the journal itself. On failure the keys go back into
the journal. Resolves rather than rejects.
Returns any
a promise of { written, upserts, deletes }, or { written: false } with error when nothing was written or the write failed
Writes every journalled key to the store, sealed; deletes what is gone.
One flush at a time per process: a call made while one is in flight waits for it and then takes the journal itself. On failure the keys go back into the journal. Resolves rather than rejects.