Currently, trust level is calculated with this formula:
`[granted_trust_level, previous_trust_level,
SiteSetting.default_trust_level].max`
When a user is invited, SiteSetting.default_invitee_trust_level should
be respected in that calculation.
There is no need to validate the user's emails when
promoting/demoting their trust level, this can cause
issues in things like Jobs::Tl3Promotions, we don't
need to fail in that case when all we are doing is changing
trust level.
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.
