Add one click unsubscribe to notification emails

[jasoncartwright]

https://support.google.com/mail/answer/81126?hl=en&sjid=17887797320169880333-EU

To set up one-click unsubscribe, include both of these headers in outgoing messages:

List-Unsubscribe-Post: List-Unsubscribe=One-Click
List-Unsubscribe: https://solarmora.com/unsubscribe/example
When a recipient unsubscribes using one-click, you receive this POST request:

"POST /unsubscribe/example HTTP/1.1
Host: solarmora.com
Content-Type: application/x-www-form-urlencoded
Content-Length: 26
List-Unsubscribe=One-Click"