* Ensure p.Integration is not nil
A Sentry crash report showed that the check
p.Integration.URL != input.integration.URL
was dereferencing a nil pointer. At that point in the code,
input.Integration is known to be non-nil, but we still need to check
whether the original, p.Integration, is.
Crash report: https://mattermost-mr.sentry.io/issues/4918263046/events/5738b67edcee4c9c883d40f7d26563a6
* Test nil original integration and both nil
https://mattermost.atlassian.net/browse/MM-52532
- Replace golint with revive
- Add makezero linter
- Fix all the required linter failures
Some issues in enterprise and public modules
are yet to be fixed. We send this to expediate things.
