Previously people were not consistent about mocking which left internals in
a fragile state when running subfolder specs.
This introduces a simple helper `set_subfolder` which you can use to set
the subfolder for the spec. It takes care of proper configuration of subfolder
and teardown.
```
# usage
set_subfolder "/my_amazing_subfolder"
```
You should no longer stub base_uri or global_settings
* Introduced fab!, a helper that creates database state for a group
It's almost identical to let_it_be, except:
1. It creates a new object for each test by default,
2. You can disable it using PREFABRICATION=0
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
