We were using the same logic in many different places, so we're
simplifying the code. I'm not convinced about the method names, though,
so we might change them in the future.
Note using this method for the default tenant in the `TenantDiskService`
class resulted in a `//` in the path, which is probably harmless but
very ugly and it also generates a different key than the one we got
until now. I've added an extra test to make sure that isn't the case.
We're using the "tenants" subfolder for consistency with the folder
structure we use in ActiveStorage and because some CONSUL installations
might have folders inside the `data` folder which might conflict with
the folders created by tenants.
Note that the Python scripts have a lot of duplication, meaning we need
to change all of them. I'm not refactoring them because I'm not familiar
enough with these scripts (or with Python, for that matter).
Also note that the scripts folder is still shared by all tenants,
meaning it isn't possible to have different scripts for different
tenants. I'm not sure how this situation should be handled; again, I'm
not familiar enough with this feature.
The scripts crashed when the `data` folder wasn't present, which is the
common situation in development environments or production environments
not using Capistrano, since this folder isn't under version control.
