Create emails

src/account/auth_pipeline.py

src/account/models.py

src/account/serializers.py

src/common/emails/admitted.txt

src/common/emails/denied.txt

src/common/emails/homework_corrected.txt

src/common/emails/new_homework.txt

src/common/emails/registration.txt

src/homework/serializers.py

src/homework/views.py