Overview of "what I have shared"

We have a convenient view of what histories are shared with us, but not what we've shared with others. This might be useful, our users often care about privacy and similar.

also from discussion with @joachimwolff

The issue does not name files, tests, or an entry point; start by locating the existing view of histories shared with the user. Define the scope for an overview of histories shared with others, including the privacy-related behavior and how completion will be verified.

Written by the indexing model from the issue text.