# What this PR does
Fixes https://github.com/grafana/oncall/issues/1103, inspired by
https://github.com/grafana/oncall/pull/1934.
Makes sure that:
1. `LiveSettings.validate_settings` is only called once per update
request and not called for any individual LiveSetting instance save.
2. `telegram.Bot.set_webhook` is only called once per request when
changing `TELEGRAM_WEBHOOK_HOST`.
## Which issue(s) this PR fixes
https://github.com/grafana/oncall/issues/1103
## Checklist
- [x] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)
* remove email verification related code
* remove email verification related code
* remove sendgrid callback
* remove sendgrid related code
* remove sendgrid related code
* rename sendgrid app to email
* remove email from built-in channels
* remove email from built-in channels
* remove email from built-in channels
* add email backend: https://github.com/grafana/oncall/pull/50
* add email templater
* add email templater
* convert md to html
* add email settings to live settings
* use task to send email, handle some exceptions to create logs
* remove ERROR_NOTIFICATION_MAIL_DELIVERY_FAILED usage
* add email limit logic
* fix tests
* add docs
* remove old email templates
* remove old email templates
* add template_fields to messaging backend
* add messaging backends templates to public api
* add comment for deprecated fields
* fix test
* fix tests
* disable email by default
* don't retry on SMTPException and TimeoutError
* add tests
* bring email back to public api docs
* return ERROR_NOTIFICATION_MAIL_LIMIT_EXCEEDED
* make template_fields tuple
* build_subject_and_title -> build_subject_and_message
* add one more comment about template deprecation
* use 8 as backend id
* add comment about gaierror and BadHeaderError
* add comment on importing in notify_user_async
* edit oss docs
