Add more precision to the order email (#51)

Reviewed-on: data.coop/membersystem#51
Co-authored-by: Benjamin Bach <benjamin@overtag.dk>
Co-committed-by: Benjamin Bach <benjamin@overtag.dk>

src/membership/templates/membership/emails/order.txt

@@ -1,6 +1,17 @@
 {% extends "membership/emails/base.txt" %}{% load i18n %}
 
-{% block content %}{% url 'order:detail' order_id=order.id as order_url %}{% blocktrans %}You have an order in our system, you can pay it here:
+{% block content %}{% url 'order:detail' order_id=order.id as order_url %}{% blocktrans %}You have an order in our system, which you can pay here:
 
 {{ protocol }}://{{ domain }}{{ order_url }}
+
+We used to handle membership stuff in a spreadsheet and via bank transfers. This is now all handled with our custom-made membership system. We hope you like it.
+
+If you received this email and no longer want a membership, you can ignore it. But please let us know by writing board@data.coop, so we can erase any personal data we have about your previous membership.
+
+Dansk:
+
+Hej! Så kører medlemsystemet endeligt! Det er mega-fedt, fordi vi længe har haft besvær med manuelle procedurer. Nu har vi flyttet medlemsdata over på members.data.coop, og betalingen fungerer. Vi kan dermed fremover arbejde stille og roligt på at integrere systemet, så man kan styre sine services via medlemssystemet.
+
+Hvis du ikke længere vil være medlem, kan du ignorere mailen her; men du må meget gerne informere os via board@data.coop, så vi kan slette evt. personlige data og services, du har kørende på dit tidligere medlemskab.
+
 {% endblocktrans %}{% endblock %}