lib.backup() ran its originals one at a time, so the content pool's five
slots, or the contentConcurrency of the pools a library was opened with,
went unused. The work for one original, its verify hashing included, is
now storeOriginal, and that many workers take files from one iterator
over the backup's files, so no more originals than the limit are open at
once. BackupLibrary gains contentConcurrency, which the library sets from
its content pool. The README's "Request pools" says so. The tests of a
backup whose lock is lost now expect all three originals downloaded,
since all three are under way at once.
Model: opus-5-5
Against the fake Ente server, with each download held until the test lets
it go: a library with the default pools has five downloads in flight and a
pool of two has two; with verify, only the originals whose downloads are
in flight have been hashed; a 404 for one photo does not stop the rest;
and two runs end the same with a pool of one as with the default pools.
Today the backup downloads one original at a time, so the first four fail.
Model: opus-5-5
sneak