The expiresAt field is populated as soon as the party is created, which will tick down while waiting for another player to join and start the duel. The logic should be updated so that expiresAt is set to NULL when the party is created and is only set to StandardizedOffsetDateTime.now() when the duel is started.

QA:

• SSE endpoint indicates that expiresAt is NULL after party is created
• SSE endpoint indicates that expiresAt is populated after duel is started