fix: Make UnionCredentialsExtractor tolerate failures.

Fixes https://github.com/solid/community-server/issues/1031

test/unit/util/errors/HttpErrorUtil.test.ts

@@ -0,0 +1,50 @@
+import { HttpError } from '../../../../src/util/errors/HttpError';
+import { createAggregateError, getStatusCode } from '../../../../src/util/errors/HttpErrorUtil';
+import { NotFoundHttpError } from '../../../../src/util/errors/NotFoundHttpError';
+
+describe('ErrorUtil', (): void => {
+  describe('createAggregateError', (): void => {
+    const error401 = new HttpError(401, 'UnauthorizedHttpError');
+    const error415 = new HttpError(415, 'UnsupportedMediaTypeHttpError');
+    const error501 = new HttpError(501, 'NotImplementedHttpError');
+    const error = new Error('noStatusCode');
+
+    it('throws an error with matching status code if all errors have the same.', async(): Promise<void> => {
+      expect(createAggregateError([ error401, error401 ])).toMatchObject({
+        statusCode: 401,
+        name: 'UnauthorizedHttpError',
+      });
+    });
+
+    it('throws an InternalServerError if one of the errors has status code 5xx.', async(): Promise<void> => {
+      expect(createAggregateError([ error401, error501 ])).toMatchObject({
+        statusCode: 500,
+        name: 'InternalServerError',
+      });
+    });
+
+    it('throws an BadRequestHttpError if all handlers have 4xx status codes.', async(): Promise<void> => {
+      expect(createAggregateError([ error401, error415 ])).toMatchObject({
+        statusCode: 400,
+        name: 'BadRequestHttpError',
+      });
+    });
+
+    it('interprets non-HTTP errors as internal errors.', async(): Promise<void> => {
+      expect(createAggregateError([ error ])).toMatchObject({
+        statusCode: 500,
+        name: 'InternalServerError',
+      });
+    });
+  });
+
+  describe('#getStatusCode', (): void => {
+    it('returns the corresponding status code for HttpErrors.', async(): Promise<void> => {
+      expect(getStatusCode(new NotFoundHttpError())).toBe(404);
+    });
+
+    it('returns 500 for other errors.', async(): Promise<void> => {
+      expect(getStatusCode(new Error('404'))).toBe(500);
+    });
+  });
+});