Remove hardcoded URLs from (mail/bot) templates

[stefan2904]

At the moment, there are many hardcoded "weilsumwasgeht.at URLs in the mailtemplates (in templates/emails).

Consider replacing all hardcoded URLs by calls to Django's url tag (or a own tag). In addition, set global SITE_URL in settings.py and use to build urls in templates.
Also, remove hardcoded value from utils.make_absolute_url().

Quickfix: replace all hardcoded URLs by new hardcoded URLs ...

[stefan2904]

(This is necessary since we probably move the app from weilsumwasgeht.at to mitmachen.vdb.at. Furthermore, it should be able to redeploy it to other hosts without changing all the templates.)

[benfreu]

Please be careful with utils.make_absolute_url()

It's called from email templates that get generated outside a request context so it can't use Django's own url generation function. make_absolute_url needs a hard coded value, but it should indeed be moved to the settings, true.

[stefan2904]

@benfreu jep, deswegen wollen wir die Funktion auch verwenden und nicht ändern. (Bis aufs verschieben von der Konstante).

[stefan2904]

🚩 🔝🔜
This issue is now even more important, since we deployed on the new domain today which broke all URLs in mails ...