Change Members::ActivityService to use user timezone

What does this MR do and why?

This MR changes the Members::ActivityService to use the user's timezone when creating a lease in Redis.

Previously, we would create a lease until midnight UTC to prevent multiple updates for the same user in a single day.

This had a side effect that meant at midnight UTC, we would see a large increase in the number of activities being recorded again.

This change mitigates that slightly in that it will attempt to use the user's timezone, creating a lease until midnight in their time zone instead.

If a user does not have a timezone set, user.timezone will be nil and it will fall back to UTC as it was before.

Refs #479114 (closed)

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