OptionalifMatch: stringOne kept version (<path>/history/<revision>).
OptionalifNoneMatch: stringConditional upload: ifMatch updates exactly that version; create sends If-None-Match: *.
A mismatch throws an HttpError with code precondition_failed (412).
Optionalsignal: AbortSignal
One blob:
vaults/<id>(JWT) ordatabases/<id>(legacy).