Clean up and simplify magic links

app/models/identity.rb

@@ -1,11 +1,32 @@
 class Identity < UntenantedRecord
-  # This is used to instantiate an Identity-like object from the `identity_token` without hitting
-  # the untenanted database. It is intended to be used with caching/etagging methods.
-  Mock = Struct.new(:id, :updated_at) do
-    def identity
-      Identity.find_signed(id)
+  has_many :memberships, dependent: :destroy
+  has_many :magic_links, dependent: :delete_all
+
+  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
 
-  has_many :memberships, dependent: :destroy
+  def send_magic_link
+    magic_links.create!.tap do |magic_link|
+      MagicLinkMailer.sign_in_instructions(magic_link).deliver_later
+    end
+  end
+
+  def link_to(tenant)
+    memberships.find_or_create_by!(tenant: tenant) do |membership|
+      membership.account_name = ApplicationRecord.with_tenant(membership.tenant) { Account.sole.name }
+    end
+  end
+
+  def unlink_from(tenant)
+    memberships.find_by(tenant: tenant)&.destroy
+  end
 end