feat(v2): auto-generated sidebars, frontmatter-less sites (#4582)

* POC of autogenerated sidebars

* use combine-promises utility lib

* autogenerated sidebar poc working

* Revert "autogenerated sidebar poc working"

This reverts commit c81da980

* POC of auto-generated sidebars for community docs

* update tests

* add initial test suite for autogenerated sidebars + fix some edge cases

* Improve autogen sidebars: strip more number prefixes in folder breadcrumb + slugs

* fix typo!

* Add tests for partially generated sidebars + fix edge cases + extract sidebar generation code

* Ability to read category metadatas file from a file in the category

* fix tests

* change position of API

* ability to extract number prefix

* stable system to enable position frontmatter

* fix tests for autogen sidebar position

* renamings

* restore community sidebars

* rename frontmatter position -> sidebar_position

* make sidebarItemsGenerator fn configurable

* minor changes

* rename dirPath => dirName

* Make the init template use autogenerated sidebars

* fix options

* fix docusaurus site: remove test docs

* add _category_ file to docs pathsToWatch

* add _category_ file to docs pathsToWatch

* tutorial: use sidebar_position instead of file number prefixes

* Adapt Docusaurus tutorial for autogenerated sidebars

* remove slug: /

* polish the homepage template

* rename _category_ sidebar_position to just "position"

* test for custom sidebarItemsGenerator fn

* fix category metadata + add link to report tutorial issues

* fix absolute path breaking tests

* fix absolute path breaking tests

* Add test for floating number sidebar_position

* add sidebarItemsGenerator unit tests

* add processSidebars unit tests

* Fix init template broken links

* windows test

* increase code translations test timeout

* cleanup mockCategoryMetadataFiles after windows test fixed

* update init template positions

* fix windows tests

* fix comment

* Add autogenerated sidebar items documentation + rewrite the full sidebars page doc

* add useful comment

* fix code block title

packages/docusaurus-plugin-content-docs/src/__tests__/options.test.ts

@@ -7,6 +7,7 @@
 
 import {OptionsSchema, DEFAULT_OPTIONS} from '../options';
 import {normalizePluginOptions} from '@docusaurus/utils-validation';
+import {DefaultSidebarItemsGenerator} from '../sidebarItemsGenerator';
 
 // the type of remark/rehype plugins is function
 const markdownPluginsFunctionStub = () => {};
@@ -26,6 +27,7 @@ describe('normalizeDocsPluginOptions', () => {
       homePageId: 'home', // Document id for docs home page.
       include: ['**/*.{md,mdx}'], // Extensions to include.
       sidebarPath: 'my-sidebar', // Path to sidebar configuration for showing a list of markdown pages.
+      sidebarItemsGenerator: DefaultSidebarItemsGenerator,
       docLayoutComponent: '@theme/DocPage',
       docItemComponent: '@theme/DocItem',
       remarkPlugins: [markdownPluginsObjectStub],