Settings export refactor (#1646)

* Refactor Export to take an account and know about the export types

* Use Export instance in settings/exports#show

app/models/export.rb

@@ -2,13 +2,43 @@
 require 'csv'
 
 class Export
-  attr_reader :accounts
+  attr_reader :account
 
-  def initialize(accounts)
-    @accounts = accounts
+  def initialize(account)
+    @account = account
   end
 
-  def to_csv
+  def to_blocked_accounts_csv
+    to_csv account.blocking
+  end
+
+  def to_muted_accounts_csv
+    to_csv account.muting
+  end
+
+  def to_following_accounts_csv
+    to_csv account.following
+  end
+
+  def total_storage
+    account.media_attachments.sum(:file_file_size)
+  end
+
+  def total_follows
+    account.following.count
+  end
+
+  def total_blocks
+    account.blocking.count
+  end
+
+  def total_mutes
+    account.muting.count
+  end
+
+  private
+
+  def to_csv(accounts)
     CSV.generate do |csv|
       accounts.each do |account|
         csv << [(account.local? ? account.local_username_and_domain : account.acct)]