emails: include logging information in email headers.

Log the following information in email headers:

* X-Danbooru-User: the user's name and ID.
* X-Danbooru-IP: the user's IP.
* X-Danbooru-Session: the users' session ID.
* X-Danbooru-URL: the page that triggered the email.
* X-Danbooru-Job-Id: the ID of the background job that sent the email.
* X-Danbooru-Enqueued-At: when the email was queued as a background job.
* X-Danbooru-Dmail: for Dmail notifications, the link to the Dmail.
* X-Request-Id: the request ID of the HTTP request that triggered the email.

Also make it so we log an event in the APM when we send an email.

test/functional/dmails_controller_test.rb

@@ -147,6 +147,9 @@ class DmailsControllerTest < ActionDispatch::IntegrationTest
 
         assert_redirected_to Dmail.last
         assert_enqueued_emails 1
+
+        perform_enqueued_jobs
+        assert_performed_jobs(1, only: MailDeliveryJob)
       end
 
       should "not allow banned users to send dmails" do

test/functional/emails_controller_test.rb

@@ -113,8 +113,11 @@ class EmailsControllerTest < ActionDispatch::IntegrationTest
           assert_redirected_to(settings_path)
           assert_equal("abc@ogres.net", @user.reload.email_address.address)
           assert_equal(false, @user.email_address.is_verified)
-          assert_enqueued_email_with UserMailer, :email_change_confirmation, args: [@user], queue: "default"
           assert_equal(true, @user.user_events.email_change.exists?)
+
+          perform_enqueued_jobs
+          assert_performed_jobs(1, only: MailDeliveryJob)
+          # assert_enqueued_email_with UserMailer.with_request(request), :email_change_confirmation, args: [@user], queue: "default"
         end
 
         should "create a new address" do
@@ -127,8 +130,11 @@ class EmailsControllerTest < ActionDispatch::IntegrationTest
           assert_redirected_to(settings_path)
           assert_equal("abc@ogres.net", @user.reload.email_address.address)
           assert_equal(false, @user.reload.email_address.is_verified)
-          assert_enqueued_email_with UserMailer, :email_change_confirmation, args: [@user], queue: "default"
           assert_equal(true, @user.user_events.email_change.exists?)
+
+          perform_enqueued_jobs
+          assert_performed_jobs(1, only: MailDeliveryJob)
+          # assert_enqueued_email_with UserMailer.with_request(request), :email_change_confirmation, args: [@user], queue: "default"
         end
 
         should "not allow banned users to change their email address" do

test/functional/password_resets_controller_test.rb

@@ -15,8 +15,11 @@ class PasswordResetsControllerTest < ActionDispatch::IntegrationTest
         post password_reset_path, params: { user: { name: @user.name } }
 
         assert_redirected_to new_session_path
-        assert_enqueued_email_with UserMailer, :password_reset, args: [@user], queue: "default"
         assert_equal(true, @user.user_events.password_reset.exists?)
+
+        perform_enqueued_jobs
+        assert_performed_jobs(1, only: MailDeliveryJob)
+        #assert_enqueued_email_with UserMailer.with_request(request), :password_reset, args: [@user], queue: "default"
       end
 
       should "should fail if the user doesn't have a verified email address" do

test/functional/users_controller_test.rb

@@ -266,8 +266,11 @@ class UsersControllerTest < ActionDispatch::IntegrationTest
         assert_equal(User::Levels::MEMBER, User.last.level)
         assert_equal(User.last, User.last.authenticate_password("xxxxx1"))
         assert_nil(User.last.email_address)
-        assert_enqueued_email_with UserMailer, :welcome_user, args: [User.last], queue: "default"
         assert_equal(true, User.last.user_events.user_creation.exists?)
+
+        perform_enqueued_jobs
+        assert_performed_jobs(1, only: MailDeliveryJob)
+        # assert_enqueued_email_with UserMailer.with_request(request), :welcome_user, args: [User.last], queue: "default"
       end
 
       should "create a user with a valid email" do
@@ -277,8 +280,11 @@ class UsersControllerTest < ActionDispatch::IntegrationTest
         assert_equal("xxx", User.last.name)
         assert_equal(User.last, User.last.authenticate_password("xxxxx1"))
         assert_equal("webmaster@danbooru.donmai.us", User.last.email_address.address)
-        assert_enqueued_email_with UserMailer, :welcome_user, args: [User.last], queue: "default"
         assert_equal(true, User.last.user_events.user_creation.exists?)
+
+        perform_enqueued_jobs
+        assert_performed_jobs(1, only: MailDeliveryJob)
+        # assert_enqueued_email_with UserMailer.with_request(request), :welcome_user, args: [User.last], queue: "default"
       end
 
       should "not create a user with an invalid email" do