Support ASC/DESC ordering in index/composite index definitions

[masatoi]

Problem

Currently, Mito does not seem to support specifying the sort order (ASC or DESC) for columns within an index definition. It appears that deftable only accepts a list of column names (symbols or strings) for :keys and :unique-keys.

When dealing with large tables, it is often necessary to create composite indexes with mixed sort orders (e.g., (category_id ASC, score DESC)) to optimize specific queries (e.g., ORDER BY category_id ASC, score DESC).

Current Limitation
If I attempt to pass a list specifying the order, such as (:desc :score), Mito raises an error because the current implementation expects simple column names.

Proposed Feature

It would be great if Mito could support a syntax to specify the sort order in deftable (or defclass).

Example Syntax:

(mito:deftable user-scores ()
  ((user-id :col-type :bigint)
   (score   :col-type :integer)
   (created-at :col-type :timestamp))
  ;; Proposal: Allow (:desc column-name) or (:asc column-name) in keys
  (:keys (user-id (:desc score))))

Expected SQL (e.g. MySQL/PostgreSQL):

CREATE INDEX index_name ON user_scores (user_id, score DESC);