Add portal info to "request to join group" email

[adamhgriffith-uofu]

For non-production Portals.

Add information to mailgun() in ./portal/views.py clarifying from which Portal server the request originated.

r = requests.post("https://api.mailgun.net/v3/slateci.io/messages",
        auth=('api', mailgun_api_token),
        data={
            "from": "SLATE <[email protected]>",
            "to": [admin_email],
            "cc": "{} <{}>".format(user_name, user_email),
            "subject": "Request to Join Group: {}".format(group_name),
            "text": "Hello! User, {}, is CC'd on this email {}, and has requested to join your group, {} on SLATE. You may choose to add them from your groups detailed page through the SLATE portal.".format(user_name, user_email,group_name)
        })

[Mannuel25]

Hello @adamhgriffith-uofu I'd love to work on this. But could you put me through as to what should be done. Thanks