Ensures that `UserStat#post_count` and `UserStat#topic_count` does not
go below 0. When it does like it did now, we tend to have bugs in our
code since we're usually coding with the assumption that the count isn't
negative.
In order to support the constraints, our post and topic fabricators in
tests will now automatically increment the count for the respective
user's `UserStat` as well. We have to do this because our fabricators
bypasss `PostCreator` which holds the responsibility of updating `UserStat#post_count` and
`UserStat#topic_count`.
This is intended for use by plugins which are building their own topic lists, and want to include PMs alongside regular topics (e.g. discourse-assign). It does not get used directly in core.
This change both speeds up specs (less strings to allocate) and helps catch
cases where methods in Discourse are mutating inputs.
Overall we will be migrating everything to use #frozen_string_literal: true
it will take a while, but this is the first and safest move in this direction
This updates tests to use latest rails 5 practice
and updates ALL dependencies that could be updated
Performance testing shows that performance has not regressed
if anything it is marginally faster now.
