Create separate section for column attributes

[pathscale]

Background

For now there are primary_key, primary key type (autoincrement/custom) and optional.

Problem to solve

Add separate section for attributes for better usability.

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Migrated from pathscale/wt-dead#1. Originally opened by @Handy-caT on 2024-09-30T18:14:16Z.

[pathscale]

Valid pre-1.0 compatibility decision. The parser still has a TODO to move attributes, and current column modifiers are inline. Acceptance is either implement the separate section with migration/compile-fail coverage before freezing the DSL, or explicitly keep inline modifiers as the 1.0 grammar and close this request as not planned.

[pathscale]

PR #46 does not alter the column-attribute grammar. The parser still carries the TODO to move attributes to a separate section, while modifiers remain inline. Because the proposed separate syntax is not specified, there is no meaningful compile probe beyond confirming absence; this remains a pre-1.0 compatibility decision rather than a reproduced runtime bug.

[pathscale]

Closed by the explicit 1.0 grammar decision implemented in #47. Column modifiers remain inline, and a separate attributes section is rejected with an actionable migration diagnostic and compile-level test. This syntax will not be added for 1.0.