[Enhancement] SQL: Chats, Average conversation time (min)

[JaanikaTalvistu]

MODULE: Analytics
SCOPE: Chats
SQL: DSL/Resql/analytics/POST/chat-avg-duration.sql

Acceptance Criteria

• Counted chats need to have an ENDED status (as-is).
• Only unique chats are taken into account (as-is).
• Calculation is from the most recent message created - the oldest message created (as-is).
• Only average is used (as-is).
• Test chats are excluded (as-is).

[JaanikaTalvistu]

Checked SQL, nothing to adjust here.