Remove the internal API

* Bind sessions to identities
* Remove references to the identity token
* Move email changes to identity
* Move account menu into a turbo-frame
* Create tenants from a tenanted route

app/models/identity.rb

@@ -1,18 +1,12 @@
 class Identity < UntenantedRecord
+  include EmailAddressChangeable, Transferable
+
   has_many :memberships, dependent: :destroy
-  has_many :magic_links, dependent: :delete_all
+  has_many :magic_links, dependent: :destroy
+  has_many :sessions, dependent: :destroy
 
   normalizes :email_address, with: ->(value) { value.strip.downcase }
-
-  class << self
-    def link(email_address:, to:)
-      find_or_create_by!(email_address: email_address).tap { |identity| identity.link_to(to) }
-    end
-
-    def unlink(email_address:, from:)
-      find_by(email_address: email_address)&.unlink_from(from)
-    end
-  end
+  validates :email_address, presence: true
 
   def send_magic_link
     magic_links.create!.tap do |magic_link|
@@ -20,13 +14,17 @@ class Identity < UntenantedRecord
     end
   end
 
-  def link_to(tenant)
+  def link_to(tenant, context: nil)
     memberships.find_or_create_by!(tenant: tenant) do |membership|
-      membership.account_name = ApplicationRecord.with_tenant(membership.tenant) { Account.sole.name }
+      membership.context = context
     end
   end
 
   def unlink_from(tenant)
     memberships.find_by(tenant: tenant)&.destroy
   end
+
+  def staff?
+    email_address.ends_with?("@37signals.com") || email_address.ends_with?("@basecamp.com")
+  end
 end