Latest redis interoduces a block form of multi / pipelined, this was incorrectly
passed through and not namespaced.
Fix also updates logster, we held off on upgrading it due to missing functions
* DEV: add testing for multi del on keys
Following #15905 we were missing some tests, this covers cases where
del is used in the form of .del(key1,key2)
It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
