Streaming: refactor to custom Error classes (#28632)

Co-authored-by: Renaud Chaput <renchap@gmail.com>
Co-authored-by: Claire <claire.github-309c@sitedethib.com>

streaming/errors.js

@@ -0,0 +1,51 @@
+// @ts-check
+
+/**
+ * Typed as a string because otherwise it's a const string, which means we can't
+ * override it in let statements.
+ * @type {string}
+ */
+const UNEXPECTED_ERROR_MESSAGE = 'An unexpected error occurred';
+exports.UNKNOWN_ERROR_MESSAGE = UNEXPECTED_ERROR_MESSAGE;
+
+/**
+ * Extracts the status and message properties from the error object, if
+ * available for public use. The `unknown` is for catch statements
+ * @param {Error | AuthenticationError | RequestError | unknown} err
+ */
+exports.extractStatusAndMessage = function(err) {
+  let statusCode = 500;
+  let errorMessage = UNEXPECTED_ERROR_MESSAGE;
+  if (err instanceof AuthenticationError || err instanceof RequestError) {
+    statusCode = err.status;
+    errorMessage = err.message;
+  }
+
+  return { statusCode, errorMessage };
+};
+
+class RequestError extends Error {
+  /**
+   * @param {string} message
+   */
+  constructor(message) {
+    super(message);
+    this.name = "RequestError";
+    this.status = 400;
+  }
+}
+
+exports.RequestError = RequestError;
+
+class AuthenticationError extends Error {
+  /**
+   * @param {string} message
+   */
+  constructor(message) {
+    super(message);
+    this.name = "AuthenticationError";
+    this.status = 401;
+  }
+}
+
+exports.AuthenticationError = AuthenticationError;