Currently, change messages posted on behalf of another user lead to
confusion when they are displayed in the UI. One example is that the CI
removes a user's vote on behalf of them. This makes it look like they
removed it themselves which is not intended.
The new realAuthor field will let the UI display this in a more
understandable way for the user.
Change-Id: I9080ae3ed7aaa9b61501c093cee3dd7f02768d49
9221ef1a3e