Allow a self-hosted user to configure their SMTP settings directly from within the UI (#682)

* Add setting fields to model

* Allow to configure SMTP settings

* Normalize locales

* Cleanup locales

* Remove 'coming soon'

* fix test

* Reset credentials

* Reset development config

* Check smtp spelling

* Use post instead of get method

* TLS ENV variable is more descriptive

* Rework application mailer

* Follow rails convention for mailer action params

* Reset schema.rb to main

* Test WIP

* Add test for controller and mailer

* Move tests from controller to model

* Custom error message if settings are not all present

* Comment smtp config in development env

* Add default tls enabled value

* Rubocop

* Fix controller test

* Reset credentials

* Normalize locales

* Test

* fix test

* Fix application mailer test that fails randomly

* Error flash message instead of notice

* Rework application mailer tests

.env.example

@@ -9,7 +9,10 @@ SMTP_ADDRESS=
 SMTP_PORT=465
 SMTP_USERNAME=
 SMTP_PASSWORD=
-TLS=true
+SMTP_TLS_ENABLED=true
+
+# Email Configuration
+EMAIL_SENDER=
 
 # Database Configuration
 DB_HOST=localhost # May need to be changed to `DB_HOST=db` if using devcontainer