List of joined/created study sessions

[orz9]

Add in "/mysession" function

This function allows users to see the sessions they have joined/created.

This will also allows users to make changes to the sessions.

If the user is the initiator, they will be allowed to:

1. Modify the date, time, location
2. Cancel the session
   Every modification will generate a system message which will be sent to all students who joined the same session.

If the user is the joiner, they will be allowed to:

1. Leave the session
   The program will ask the user to key in reasons for leave the session, and then the system will send message to the initiator of the study session.

Sample of program flow:

• "Could you share with us about your reason of leaving the session?"
• System receives the reason keyed in by the user, stores it in the variable names "reasons"
• Initiator will receive:
  "We are sorry to inform you that @tele_handle has left your study session."
  "Reason of leaving: xxxx"