feat: kick user duplicated connections

[apsantiso]

This PR implements user duplicate connection prevention. If a user tries to connect to a call with duplicate connections, the oldest one is kicked.

• Received a webhook with a recent connection -> oldest connection gets kicked -> recent connection is saved
• Received a webhook with an old connection -> old connection is kicked -> recent connection remains (nothing saved here)
• User tries to join while having another connection -> previous connections is kicked