Add DMCA complaint form.

Add a form for submitting DMCA complaints. The complaint is emailed to
the site owner, and a confirmation email is sent to the submitter.

test/mailers/previews/user_mailer_preview.rb

@@ -1,21 +1,36 @@
 class UserMailerPreview < ActionMailer::Preview
   def dmail_notice
-    dmail = User.system.dmails.first
+    user = params[:id].present? ? User.find(params[:id]) : User.owner
+    dmail = Dmail.received.order(id: :desc).offset(279).first
     UserMailer.dmail_notice(dmail)
   end
 
   def password_reset
-    user = User.find(params[:id])
+    user = params[:id].present? ? User.find(params[:id]) : User.owner
     UserMailer.password_reset(user)
   end
 
   def email_change_confirmation
-    user = User.find(params[:id])
+    user = params[:id].present? ? User.find(params[:id]) : User.owner
     UserMailer.email_change_confirmation(user)
   end
 
   def welcome_user
-    user = User.find(params[:id])
+    user = params[:id].present? ? User.find(params[:id]) : User.owner
     UserMailer.welcome_user(user)
   end
+
+  def dmca_complaint
+    dmca = {
+      name: "John Doe",
+      email: "test@example.com",
+      address: "123 Fake Street",
+      infringing_urls: "https://example.com/1.html\nhttps://example.com/2.html",
+      original_urls: "https://google.com/1.html\nhttps://google.com/2.html",
+      proof: "source: me",
+      signature: "John Doe",
+    }
+
+    UserMailer.with(dmca: dmca).dmca_complaint(to: dmca[:email])
+  end
 end