Add link to HoraireETS for each session

[mhd-hi]

For sessions containing courses, display a HoraireETS icon.

Clicking on the icon will redirect to the HoraireETS website with pre-populated parameters (session, courses).

Only display the icon for sessions that have course availability (show icon until last available session hits).

Depends on:

• HoraireETS parameters in URL
• Create endpoint to fetch last available session planifETS-backend#52