Separate style from the HTML in emails.
Email templates contain style information inside the HTML.
It creates clutter in the erb files, and is difficult to track down when changing system style.
Consider using CSS to inline formatter, for example: [[https://www.ruby-toolbox.com/categories/Inline_CSS_for_E-Mail]]
Fixes #8797 - Separate style from the HTML in emails
By using roadie-rails gem (1.1) style can be separated from email
html foramt, and absolute paths can be used.
style was separated to 'email.css'