Add Confirmed notification to Session Transitions

Problem/Motivation

In the ECA Model: Session transitions there is a notification sent to site admins when a speaker declines an accepted session. This notification triggers properly when sessions are declined, but the same message is also sent when a speaker confirms their session.

Steps to reproduce

Accept a session and deploy the notification email to the speaker which includes the one-click links for confirm/decline
If the speakers confirms or decline the same notification is sent to site admin stating the session was declined.

Proposed resolution

Add a check in the ECA component to see if the session was declined or confirmed and send the appropriate message to the site admin.

marc delay will update the ECA model and submit a PR

Remaining tasks

update ECA Model: Session transitions

User interface changes

New logic switch in ECA Model: Session transitions

API changes

None

Data model changes

None