Create pleroma.email mix task

Closes: https://git.pleroma.social/pleroma/pleroma/issues/1061

lib/mix/tasks/pleroma/email.ex

@@ -0,0 +1,25 @@
+defmodule Mix.Tasks.Pleroma.Email do
+  use Mix.Task
+
+  @shortdoc "Simple Email test"
+  @moduledoc File.read!("docs/administration/CLI_tasks/email.md")
+
+  def run(["test" | args]) do
+    Mix.Pleroma.start_pleroma()
+
+    {options, [], []} =
+      OptionParser.parse(
+        args,
+        strict: [
+          to: :string
+        ]
+      )
+
+    email = Pleroma.Emails.AdminEmail.test_email(options[:to])
+    {:ok, _} = Pleroma.Emails.Mailer.deliver(email)
+
+    Mix.shell().info(
+      "Test email has been sent to #{inspect(email.to)} from #{inspect(email.from)}"
+    )
+  end
+end

lib/pleroma/emails/admin_email.ex

@@ -7,6 +7,7 @@ defmodule Pleroma.Emails.AdminEmail do
 
   import Swoosh.Email
 
+  alias Pleroma.Config
   alias Pleroma.Web.Router.Helpers
 
   defp instance_config, do: Pleroma.Config.get(:instance)
@@ -20,6 +21,19 @@ defmodule Pleroma.Emails.AdminEmail do
     Helpers.feed_url(Pleroma.Web.Endpoint, :feed_redirect, user.id)
   end
 
+  def test_email(mail_to \\ nil) do
+    html_body = """
+    <h3>Instance Test Email</h3>
+    <p>A test email was requested. Hello. :)</p>
+    """
+
+    new()
+    |> to(mail_to || Config.get([:instance, :email]))
+    |> from({instance_name(), instance_notify_email()})
+    |> subject("Instance Test Email")
+    |> html_body(html_body)
+  end
+
   def report(to, reporter, account, statuses, comment) do
     comment_html =
       if comment do