refactor: derive api error codes from contract (WealthLedger/backend#117) (#123)

src/shared/api/problem-details.ts

@@ -1,3 +1,5 @@
+import type { components } from "./generated/schema";
+
 enum ApiErrorCode {
 	BankDependentRefunds = "BANK_DEPENDENT_REFUNDS",
 	BankIntentConflict = "BANK_INTENT_CONFLICT",
@@ -6,7 +8,6 @@ enum ApiErrorCode {
 	BankVersionConflict = "BANK_VERSION_CONFLICT",
 	BankWriteConflict = "BANK_WRITE_CONFLICT",
 	BondTickerAmbiguous = "BOND_TICKER_AMBIGUOUS",
-	Forbidden = "FORBIDDEN",
 	InvalidOperationsCursor = "INVALID_OPERATIONS_CURSOR",
 	InvalidTbankToken = "INVALID_TBANK_TOKEN",
 	NotFound = "NOT_FOUND",
@@ -16,6 +17,16 @@ enum ApiErrorCode {
 	Unauthorized = "UNAUTHORIZED",
 }
 
+/**
+Compile-time drift guard: collapses to `never` when any enum member is absent
+from the generated ProblemDetails contract, so every call site fails to build.
+*/
+type ContractApiErrorCode
+	= Exclude<
+		`${ApiErrorCode}`,
+		components["schemas"]["ProblemDetailsDto"]["code"]
+	> extends never ? ApiErrorCode : never;
+
 function apiErrorCode(error: unknown): string | undefined {
 	return typeof error === "object" && error !== null && "code" in error
 		? String(error.code)
@@ -23,7 +34,10 @@ function apiErrorCode(error: unknown): string | undefined {
 }
 
 // Incoming codes are an open wire string; unknown values retain their fallback.
-function isApiErrorCode(value: unknown, expected: ApiErrorCode): boolean {
+function isApiErrorCode(
+	value: unknown,
+	expected: ContractApiErrorCode,
+): boolean {
 	return value === expected;
 }