[server] Support configurable DAY auto-partition format yyyy-MM-dd

[gyang94]

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• I searched in the issues and found nothing similar.

Motivation

Motivation

Today, auto-partitioned tables with table.auto-partition.time-unit=DAY always use yyyyMMdd as the partition value format.

This is limiting in cases where users want DAY partitions to be organized in a more readable and conventional date form such as yyyy-MM-dd. It also aligns better with typed DATE partition values, which are naturally represented in dashed form.

Solution

Introduce a new table option:

• table.auto-partition.day-format

Supported values:

• yyyyMMdd (default, backward compatible)
• yyyy-MM-dd

Behavior:

• this option only applies when table.auto-partition.time-unit=DAY
• when set to yyyy-MM-dd, all DAY auto-partition behavior
  should use dashed format consistently:
  • auto pre-created partitions
  • manual partition creation validation
  • writer-side dynamic partition creation
  • retention / expiration logic

Anything else?

No response

Willingness to contribute

• I'm willing to submit a PR!