each share for a file can have its own write enabler secret, but the wire protocol does not support more than one

[shapr]

The wire protocol allows submitting requests that are impossible to complete.

if someone did a readv and testv and writev for some storage index and some write enabler secret, but wants to update two different shares with two different write enabler secrets, this will require multiple requests.

Either the call for readvAndTestvandWritev should allow multiple write enabler secrets, or it should not work with multiple shares.

@exarkun says: There's a place for N writes, and there's a place for 1 secret. Either they should both be N or they should both be 1.

This refers to publish.py line 286 (as of November 8 2023)

​https://github.com/tahoe-lafs/tahoe-lafs/blob/master/src/allmydata/mutable/publish.py#L285