Use a different attachments folder per tenant

While this is not strictly necessary, it can help moving the data of one
tenant to a different server or removing it.

Note we're using subfolders inside the `tenants` subfolder. If we simply
used subfolders with the schema names, if the schema names were, for
instance, language codes like `es`, `en`, `it`, ... they would conflict
with the default subfolders used by Active Storage.

config/storage.yml

@@ -1,9 +1,9 @@
 local:
-  service: Disk
+  service: TenantDisk
   root: <%= Rails.root.join("storage") %>
 
 test:
-  service: Disk
+  service: TenantDisk
   root: <%= Rails.root.join("tmp/storage") %>
 
 # s3:

lib/active_storage/service/tenant_disk_service.rb

@@ -0,0 +1,13 @@
+require "active_storage/service/disk_service"
+
+module ActiveStorage
+  class Service::TenantDiskService < Service::DiskService
+    def path_for(key)
+      if Tenant.default?
+        super
+      else
+        super.sub(root, File.join(root, "tenants", Tenant.current_schema))
+      end
+    end
+  end
+end

spec/models/attachable_spec.rb

@@ -0,0 +1,16 @@
+require "rails_helper"
+
+describe Attachable do
+  it "stores attachments for the default tenant in the default folder" do
+    file_path = build(:image).file_path
+
+    expect(file_path).to include "storage/"
+    expect(file_path).not_to include "tenants"
+  end
+
+  it "stores tenant attachments in a folder for the tenant" do
+    allow(Tenant).to receive(:current_schema).and_return("image-master")
+
+    expect(build(:image).file_path).to include "storage/tenants/image-master/"
+  end
+end