Detail maintenance a bit more

[annevk]

In particular, we probably do not want folks to change the signature field. And definitely not the id field.

The verified field is up to maintainers.

So workstreams and info fields would be up for changes? Don't see anything there that is off limits.

Aside: while we track the initial signature, we don't track join/leave dates of Workstreams other than through git blame. Is that wise?

cc @domenic @foolip

[domenic]

Hmm, in 69ed4a8 I let a signature change go through. I think that kind of thing should be OK...

[annevk]

It makes it harder for someone doing IPR review I think as they cannot just look at the latest file, but maybe that's nonetheless the case.