Add generated column exclusion options

[ragokan]

Summary

• Add insert_columns.exclude to omit database-managed fields from generated insert queries.
• Add update_columns.exclude to omit fields from generated update SET clauses while keeping them available for filters or selected output.
• Cast update_mask args to text[] so sqlc generates typed []string params instead of interface{}.

Validation

• go test ./...

[iamralch]

Thanks for putting this together, @ragokan — column exclusion for the generated INSERT/UPDATE queries is a genuinely useful addition. 👍

Heads up that I can see this is still WIP and you haven't formally asked for review, so please treat this as early design input, not a review — no rush to act on any of it.

The one thing I'd love your thoughts on before it solidifies is the config shape. Right now it's two flat exclude lists (insert_columns / update_columns). I've been wondering whether the rule is better expressed as a property of the column rather than two parallel operation lists — something like:

options:
  models:
    - name: "*"               # applies to every table
      columns:
        created_at: immutable # in INSERT, out of UPDATE
    - name: user
      columns:
        id: read_only         # out of INSERT and UPDATE

trait	INSERT	UPDATE SET
(none)	✅	✅
immutable	✅	❌
read_only	❌	❌

Why I lean this way:

• "id is never inserted" is really a fact about the column, so the rule lives on the column — and one trait replaces having to keep two exclude lists in sync.
• Reads like ORM field annotations (Ent/Prisma), so it should feel familiar.
• A "*" catch-all keeps the common "timestamps on every table" case down to one block.

Two smaller notes:

• The update_mask::text[] cast is a nice catch, independent of all the above — definitely keep it.
• Good call leaving SELECT * / RETURNING * alone; listing explicit columns there makes sqlc emit a separate per-query row struct instead of reusing the model type, so we want to stay off the read side.

All very open to pushback — happy to talk it through whenever you pick this back up.