Merge remote-tracking branch 'origin/develop' into deploy-to-production-2021-02-19-no2

* origin/develop: (233 commits)
  skip failing spec
  fix(semester-feedback-test): skip to specs only failing on GitLab-CI
  fix(certificate): place date missing comma
  feat(text-changes): email to freiwillige@aoz.ch
  fix: add heroku wkhtmltopdf gem comments as reminder when switching
  fix(semester-scope): meeting date scoped with DateTime caused day overlap
  production ci deployment - manually triggerable
  fix(migrate_to_s3): more errors rescued and log failures to yaml file
  add slugignore in order to reduce slug size on heroku
  fix(wkhtmltopdf): heroku gem did not work, so try using apt
  fix(whktmltopdf): add heroku gem to default group and move dev binaries in dev group
  strange forth and back rails migration do to the schema
  feat(deploy): add manually triggerable ci job to deploy to staging
  docs(env-vars): add some readme documentation for existing and relevant  env variables
  move email initializer to env configs because thats where it belongs
  fix: action mailer overwrites production delivery method
  add new types in shema when migrated with modern rails
  fix typo in old migration
  fix: old migration having duplicate field
  feat(coplaner-upload): xlsx file upload rake task
  ...
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