fix for stats for each date

[nikhilsinhaparseable]

update stats in manifest list in snapshot for each date load daily stats on server start
update GET /stats endpoint to accept query param
if given /stats/date={date in yyyy-mm-dd} format, date level stats is returned

Fixes #XXXX.

Description

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This PR has:

• been tested to ensure log ingestion and log query works.
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added documentation for new or modified features or behaviors.