fix(common): Export and deprecate error helpers (#901)

Author: bergundy

packages/common/src/index.ts

@@ -22,6 +22,7 @@ export * from './workflow-handle';
 export * from './deprecated-time';
 
 import * as encoding from './encoding';
+import * as helpers from './type-helpers';
 
 /**
  * Encode a UTF-8 string into a Uint8Array
@@ -42,3 +43,23 @@ export function u8(s: string): Uint8Array {
 export function str(arr: Uint8Array): string {
   return encoding.decode(arr);
 }
+
+/**
+ * Get `error.message` (or `undefined` if not present)
+ *
+ * @hidden
+ * @deprecated - meant for internal use only
+ */
+export function errorMessage(error: unknown): string | undefined {
+  return helpers.errorMessage(error);
+}
+
+/**
+ * Get `error.code` (or `undefined` if not present)
+ *
+ * @hidden
+ * @deprecated - meant for internal use only
+ */
+export function errorCode(error: unknown): string | undefined {
+  return helpers.errorCode(error);
+}