Resolve "[Info mailings] sent_to works globally instead of per event"

Closes #20

See merge request !10

Currently translated at 100.0% (235 of 235 strings)

Translation: Hack'n'Fun/AlekSIS-App-Paweljong
Translate-URL: https://translate.edugit.org/projects/hacknfun/aleksis-app-paweljong/de/

Resolve "Info mailing"

Closes #17

See merge request !9

Currently translated at 99.1% (221 of 223 strings)

Translation: Hack'n'Fun/AlekSIS-App-Paweljong
Translate-URL: https://translate.edugit.org/projects/hacknfun/aleksis-app-paweljong/de/

Fix creation of mail addresses

See merge request !8

Currently translated at 99.0% (218 of 220 strings)

Translation: Hack'n'Fun/AlekSIS-App-Paweljong
Translate-URL: https://translate.edugit.org/projects/hacknfun/aleksis-app-paweljong/de/

Currently translated at 96.0% (216 of 225 strings)

Translation: Hack'n'Fun/AlekSIS-App-Paweljong
Translate-URL: https://translate.edugit.org/projects/hacknfun/aleksis-app-paweljong/de/

Resolve "Wizard should have consistent page and browser title"

Closes #10

See merge request !5

Resolve "Slug for event must not be the short_name of the group"

Closes #7

See merge request !6

Merge branch '7-slug-for-event-must-not-be-the-short-name-of-the-group' of edugit.org:Teckids/hacknfun/AlekSIS-App-Paweljong into 7-slug-for-event-must-not-be-the-short-name-of-the-group