feat(v2): docs version configuration: lastVersion, version.{path,label} (#3357)

* add new docs versioning options

* Add some tests for new versioning options

* Add some docs for version configurations

* try to fix broken link detection after /docs/ root paths have been removed on deploy previews

* improve dev/deploypreview versioning configurations

* disable custom current version path, as it produces broken links

* readVersionDocs should not be order sensitive

* fix versions page according to versioning config

* fix versions page according to versioning config

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

@@ -36,6 +36,16 @@ describe('normalizeDocsPluginOptions', () => {
       excludeNextVersionDocs: true,
       includeCurrentVersion: false,
       disableVersioning: true,
+      versions: {
+        current: {
+          path: 'next',
+          label: 'next',
+        },
+        version1: {
+          path: 'hello',
+          label: 'world',
+        },
+      },
     };
     const {value, error} = await OptionsSchema.validate(userOptions);
     expect(value).toEqual(userOptions);
@@ -117,4 +127,32 @@ describe('normalizeDocsPluginOptions', () => {
       `"\\"remarkPlugins\\" must be an array"`,
     );
   });
+
+  test('should reject bad lastVersion', () => {
+    expect(() => {
+      normalizePluginOptions(OptionsSchema, {
+        lastVersion: false,
+      });
+    }).toThrowErrorMatchingInlineSnapshot(
+      `"\\"lastVersion\\" must be a string"`,
+    );
+  });
+
+  test('should reject bad versions', () => {
+    expect(() => {
+      normalizePluginOptions(OptionsSchema, {
+        versions: {
+          current: {
+            hey: 3,
+          },
+          version1: {
+            path: 'hello',
+            label: 'world',
+          },
+        },
+      });
+    }).toThrowErrorMatchingInlineSnapshot(
+      `"\\"versions.current.hey\\" is not allowed"`,
+    );
+  });
 });