The mirrorlist ValidateConfig test imports terraform-plugin-go/tftypes
directly to build a tfsdk.Config, so `go mod tidy` moves it from an
indirect to a direct require. Commit the tidied go.mod so the CI
go-mod-tidy pre-commit hook is green.
Expose the artifactapi remotes API's new mirrorlist field so users can
configure extra upstream mirror base URLs. The API load-balances
base_url + mirrorlist with failover.
- Add optional mirrorlist list attribute to the remote resource schema
and the remote data source (read-only).
- Wire it end-to-end: TF model, wire model (json mirrorlist,omitempty),
modelToAPI/apiToModel, and preserve null/empty list semantics to avoid
plan churn.
- Scope to rpm/deb/alpine via ValidateConfig (plan-time error on other
remote types); API 400 is the backstop.
- Docs + rpm example; unit tests for round-trip, null handling, and the
type-scoping validation.