feat(v2): blog + docs multi-instance plugins (#3204)

* stable createData namespacing + second-blog dogfooding

* Docs: support multi-instance + make community docs a separate instance

* tests: add 2nd docs instance to versioned site

* fix docs version cli tests

* fix docs versioning cli

* typo

* team: add link to my site

* better extendCli integration

* fix metadata tests

* tests for versioned site with second docs instance

* move some validation code to utils-validation

* fix missing dependency

* fix bad compiled output due to importing constants in ./client folder

* make docs tests easier to maintain

* refactors

* prevent lodash imports in client bundle

* redirect old community docs to new urls

packages/docusaurus-utils-validation/src/__tests__/validationSchemas.test.ts

@@ -0,0 +1,109 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import * as Joi from '@hapi/joi';
+
+import {
+  AdmonitionsSchema,
+  RehypePluginsSchema,
+  RemarkPluginsSchema,
+  PluginIdSchema,
+} from '../validationSchemas';
+
+function createTestHelpers({
+  schema,
+  defaultValue,
+}: {
+  schema: Joi.SchemaLike;
+  defaultValue?: unknown;
+}) {
+  function testOK(value: unknown) {
+    expect(Joi.attempt(value, schema)).toEqual(value ?? defaultValue);
+  }
+
+  function testFail(value: unknown) {
+    expect(() => Joi.attempt(value, schema)).toThrowErrorMatchingSnapshot(
+      // @ts-expect-error: seems ok at runtime, but bad typedef
+      `for value=${JSON.stringify(value)}`,
+    );
+  }
+
+  return {testOK, testFail};
+}
+
+function testMarkdownPluginSchemas(schema: Joi.SchemaLike) {
+  const {testOK, testFail} = createTestHelpers({
+    schema,
+    defaultValue: [],
+  });
+
+  testOK(undefined);
+  testOK([function () {}]);
+  testOK([[function () {}, {attr: 'val'}]]);
+  testOK([
+    [function () {}, {attr: 'val'}],
+    function () {},
+    [function () {}, {attr: 'val'}],
+  ]);
+
+  testFail(null);
+  testFail(false);
+  testFail(3);
+  testFail([null]);
+  testFail([false]);
+  testFail([3]);
+  testFail([[]]);
+  testFail([[function () {}, undefined]]);
+  testFail([[function () {}, true]]);
+}
+
+describe('validation schemas', () => {
+  test('PluginIdSchema', () => {
+    const {testOK, testFail} = createTestHelpers({
+      schema: PluginIdSchema,
+      defaultValue: 'default',
+    });
+
+    testOK(undefined);
+    testOK('docs');
+    testOK('default');
+    testOK('plugin-id_with-simple-special-chars');
+
+    testFail('/docs');
+    testFail('docs/');
+    testFail('do/cs');
+    testFail('do cs');
+    testFail(null);
+    testFail(3);
+    testFail(true);
+    testFail([]);
+  });
+
+  test('AdmonitionsSchema', () => {
+    const {testOK, testFail} = createTestHelpers({
+      schema: AdmonitionsSchema,
+      defaultValue: {},
+    });
+
+    testOK(undefined);
+    testOK({});
+    testOK({attr: 'val'});
+
+    testFail(null);
+    testFail(3);
+    testFail(true);
+    testFail([]);
+  });
+
+  test('RemarkPluginsSchema', () => {
+    testMarkdownPluginSchemas(RemarkPluginsSchema);
+  });
+
+  test('RehypePluginsSchema', () => {
+    testMarkdownPluginSchemas(RehypePluginsSchema);
+  });
+});