refactor(model): collapse coded error types into a single CodedErr

[areebahmeddd]

Summary

• replaces BadReqErr, SignValidationErr, and NotFoundErr with a single model.CodedErr, reducing duplicated error types while preserving existing response behavior
• introduces a more flexible error construction API with explicit status codes, making it easier for plugins to return different HTTP statuses without relying on concrete error types
• keeps wire compatibility unchanged, updates all existing call sites, and extends tests to verify both error codes and HTTP status mappings

Fixes #888

[Copilot]

Pull request overview

This PR refactors Beckn step error handling by collapsing multiple coded error wrapper types (BadReqErr, SignValidationErr, NotFoundErr) into a single model.CodedErr that carries both the taxonomy code and an explicit HTTP status, and updates handler dispatch + call sites to preserve existing on-wire behavior while enabling more flexible status selection.

Changes:

• Introduces model.CodedErr (+ NewCodedErr, NewBadReqErr, NewSignValidationErr, NewNotFoundErr) and updates nackBecknError to route by CodedErr.HTTPStatus().
• Updates plugins/core to construct CodedErr via the new constructors and adjusts comments/docs accordingly.
• Extends/updates tests to assert both taxonomy codes and the intended HTTP status mappings.

Reviewed changes

Copilot reviewed 32 out of 32 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
pkg/testutil/becknerr.go	Updates shared test assertion helper to assert *model.CodedErr and HTTP 400 mapping.
pkg/plugin/implementation/vcvalidator/vcvalidator.go	Switches vcvalidator NACK construction to new error constructors.
pkg/plugin/implementation/vcvalidator/vcvalidator_test.go	Updates vcvalidator tests to assert CodedErr and HTTP status values.
pkg/plugin/implementation/vcvalidator/README.md	Updates documentation to reflect CodedErr constructors/statuses.
pkg/plugin/implementation/simplekeymanager/simplekeymanager.go	Replaces SignValidation error construction with new constructors.
pkg/plugin/implementation/simplekeymanager/simplekeymanager_test.go	Updates tests to assert *model.CodedErr instead of removed types.
pkg/plugin/implementation/signvalidator/signvalidator.go	Updates signvalidator to return CodedErr via new constructors.
pkg/plugin/implementation/signvalidator/signvalidator_test.go	Updates signvalidator tests to assert CodedErr and HTTP 401 mapping.
pkg/plugin/implementation/schemavalidator/schemavalidator.go	Updates bad-request construction to new NewBadReqErr(code, err) signature.
pkg/plugin/implementation/schemav2validator/schemav2validator.go	Updates bad-request construction to new NewBadReqErr(code, err) signature.
pkg/plugin/implementation/router/router.go	Updates bad-request coded error construction for invalid routing targets.
pkg/plugin/implementation/reqmapper/reqmapper.go	Updates bad-request coded error construction for missing/invalid action.
pkg/plugin/implementation/registry/registry.go	Updates bad-request construction for marshal failures to new signature.
pkg/plugin/implementation/publisher/publisher.go	Updates bad-request coded error construction for downstream publish failures.
pkg/plugin/implementation/publisher/publisher_test.go	Updates test to assert *model.CodedErr for publish failure classification.
pkg/plugin/implementation/opapolicychecker/enforcer.go	Updates policy checker to return CodedErr via NewBadReqErr.
pkg/plugin/implementation/opapolicychecker/enforcer_test.go	Updates OPA tests to assert *model.CodedErr instead of removed types.
pkg/plugin/implementation/keymanager/keymanager.go	Replaces SignValidation error construction with new constructors.
pkg/plugin/implementation/keymanager/keymanager_test.go	Updates tests to assert *model.CodedErr instead of removed types.
pkg/plugin/implementation/encrypter/encrypter.go	Updates error construction to use NewBadReqErr(code, err) signature.
pkg/plugin/implementation/decrypter/decrypter.go	Updates error construction to use NewBadReqErr(code, err) signature.
pkg/model/model.go	Updates WrapExtractContextErr to return *CodedErr and use new constructor.
pkg/model/error.go	Introduces CodedErr + constructors and updates BecknErrorer guidance.
pkg/model/error_test.go	Updates/extends tests for new CodedErr behavior and status mapping.
core/module/module_test.go	Updates policy checker mock to use new NewBadReqErr(code, err) signature.
core/module/handler/step.go	Updates bad-request/sign-validation error construction to new signatures.
core/module/handler/step_test.go	Updates tests to assert *model.CodedErr and status for schema/sign validation.
core/module/handler/stdHandler.go	Updates body-read failure to new NewBadReqErr(code, err) signature.
core/module/handler/stdHandler_test.go	Updates failing step mock to new NewBadReqErr(code, err) signature.
core/module/handler/responsestep.go	Refactors NACK dispatch to use *model.CodedErr + HTTPStatus() instead of type-switching old error types.
core/module/handler/responsestep_test.go	Updates response-step tests to new constructors and expected status mappings.
cmd/adapter/main_test.go	Updates adapter test policy checker stub to new NewBadReqErr(code, err) signature.

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[areebahmeddd]

Deliberately skipped

• didn't migrate the 59 call sites to NewCodedErr since the helper constructors preserve existing message prefixes and changing them would alter NACK text on the wire
• didn't touch SchemaValidationErr or AckNoCallbackErr since they differ in structure, not just status
• didn't change vcvalidator returning 401 for network failures since that's covered by encrypter/decrypter/publisher/vcvalidator: classify BadReqErr usage into correct codes #870 encrypter/decrypter/publisher/vcvalidator: classify BadReqErr usage into correct codes #884
  left a note that it's now a one-line change there
• didn't change the "Signature Validation Error: " prefix for non-signature causes for the same reason and the original deferral still applies

One behavior difference

• the old dispatch selected by type priority (SignValidationErr > BadReqErr > NotFoundErr) regardless of wrapping depth. the new dispatch uses the outermost CodedErr
• this only matters if an error chain contains multiple CodedErrs. traced every path and none do today, so the behavior is currently unreachable

Loose thread

• NewNotFoundErr has no production callers, only tests. it may be dead code

[Copilot]

Pull request overview

Copilot reviewed 32 out of 32 changed files in this pull request and generated no new comments.

Suppressed comments (1)

pkg/model/error.go:232

• CodedErr.Error() is documented as avoiding panics while building a NACK, but it can still panic if the receiver is nil (typed-nil *CodedErr stored in an error interface) or if the wrapped cause is a typed-nil error whose Error() dereferences a nil pointer. Making Error() nil-safe and panic-safe here prevents a request from crashing the handler during NACK rendering.

func (e *CodedErr) Error() string {
	if e.error == nil {
		return ""
	}
	return e.error.Error()