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.

app/controllers/dmcas_controller.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class DmcasController < ApplicationController
+  def create
+    @dmca = params[:dmca].slice(:name, :email, :address, :infringing_urls, :original_urls, :proof, :perjury_agree, :good_faith_agree, :signature)
+    UserMailer.with_request(request, dmca: @dmca).dmca_complaint(to: Danbooru.config.dmca_email).deliver_now
+    UserMailer.with_request(request, dmca: @dmca).dmca_complaint(to: @dmca[:email]).deliver_now
+  end
+
+  def show
+  end
+
+  def template
+  end
+end