Drop Current.account and just use Account.sole

I had reintroduced this in dacb53b8 after David removed it in
6bbf68a4, but now I agree we don't need it.

Also, fix a CORS error when trying to redirect a user to an untenanted
path after login (see
https://fizzy.37signals.com/5986089/collections/2/cards/1032).

script/bootstrap-signal-id.rb

@@ -15,7 +15,7 @@ class BootstrapSignalId
         puts "\n# tenant: #{tenant}"
 
         next unless check_account_preconditions
-        create_signal_id_account if Account.first.queenbee_id.nil?
+        create_signal_id_account if Account.sole.queenbee_id.nil?
 
         create_signal_id_users
       end
@@ -42,7 +42,7 @@ class BootstrapSignalId
       signal_id_account = SignalId::Account.find_by!(queenbee_id: queenbee_account.id)
       signal_id_account.update_column :subdomain, ApplicationRecord.current_tenant
 
-      account = Account.first
+      account = Account.sole
       account.queenbee_id = queenbee_account.id
       account.name = ApplicationRecord.current_tenant
       account.save!
@@ -50,7 +50,7 @@ class BootstrapSignalId
   end
 
   def create_signal_id_users
-    signal_account = Account.first.signal_account
+    signal_account = Account.sole.signal_account
 
     User.find_each do |user|
       if !user.system? && user.signal_user_id.nil?

script/closureulate/collections_and_cards.rb

@@ -4,7 +4,7 @@ COLLECTIONS_COUNT = 100
 CARDS_PER_COLLECTION = 50
 
 ApplicationRecord.current_tenant = "development-tenant"
-account = Account.first
+account = Account.sole
 user = account.users.first
 Current.session = user.sessions.last
 workflow = account.workflows.first

script/create-accounts-in-staging.rb

@@ -3,7 +3,7 @@
 require_relative "../config/environment"
 
 ApplicationRecord.with_each_tenant do |tenant|
-  account = Account.first
+  account = Account.sole
   signal_account = account.signal_account
 
   signal_users = SignalId::User.where(account_id: signal_account.id)

script/migrate-content-to-slugged-urls.rb

@@ -25,7 +25,7 @@ def fix_attachments(rich_text)
 end
 
 ApplicationRecord.with_each_tenant do |tenant|
-  account_id = Account.first.queenbee_id
+  account_id = Account.sole.queenbee_id
 
   unless account_id
     puts "Skipping URL fixup for tenant: #{tenant}"
@@ -37,7 +37,7 @@ ApplicationRecord.with_each_tenant do |tenant|
   domain = domains[Rails.env] || domains["production"]
   regex = %r{://\w+\.#{domain}/}
 
-  pp [ Account.first.name, account_id, domain, regex ]
+  pp [ Account.sole.name, account_id, domain, regex ]
   puts
 
   Card.find_each do |card|

script/populate/cards_for_pagination.rb

@@ -3,7 +3,7 @@ require_relative "../../config/environment"
 CARDS_COUNT = 200
 
 ApplicationRecord.current_tenant = "37signals"
-account = Account.first
+account = Account.sole
 user = User.first
 Current.session = user.sessions.last
 collection = Collection.first

script/rename-tenants-to-qb-account-id.rb

@@ -7,7 +7,7 @@ tenant_names = []
 ApplicationRecord.with_each_tenant do |tenant|
   next if tenant == "#{Rails.env}-tenant"
 
-  account = Account.first
+  account = Account.sole
   queenbee_id = account.queenbee_id
   tenant_names << { from: tenant, to: queenbee_id }