This is a follow-up to #19388.
We will in the future allow patch requests to change the visibility
of an existing topic, so `last_updated` is better name for this field.
This commit does not affect the API or events in any way, but only the
database.
This fixes a batch of mypy errors of the following format:
'Item "None" of "Optional[Something]" has no attribute "abc"
Since we have already been recklessly using these attritbutes
in the tests, adding assertions beforehand is justified presuming
that they oughtn't to be None.
This renames the test file for muting to have
the term `topic` in it, along with an ambiguously
named helper.
This is a prep change for implementing the mute
users feature.
Anders Kaseorg
Abhijeet Prasad Bodas
PIG208