Add external links override support (#2730)

* feat: add external links override support

* fix: add note, fix 404 url and fix unrelated typo

* test: fix

docs/how_tos/override-external-urls.rst

@@ -0,0 +1,80 @@
+Override External URLs
+======================
+
+What is getExternalLinkUrl?
+---------------------------
+
+The `getExternalLinkUrl` function is a utility from `@edx/frontend-platform` that allows for centralized management of external URLs. It enables the override of external links through configuration, making it possible to customize external references without modifying the source code directly.
+
+URLs wrapped with getExternalLinkUrl
+------------------------------------
+Use cases:
+
+1. **Accessibility Page** (`src/accessibility-page/AccessibilityPage.jsx`)
+   - `COMMUNITY_ACCESSIBILITY_LINK` - Points to community accessibility resources: https://www.edx.org/accessibility
+
+2. **Course Outline** (if applicable)
+   - Documentation links
+   - Help resources
+
+3. **Other pages** (search for `getExternalLinkUrl` usage across the codebase)
+   - Help documentation
+   - External tool integrations
+
+Following external URLs are wrapped with `getExternalLinkUrl` in the authoring application:
+
+- 'https://www.edx.org/accessibility'
+- 'https://docs.openedx.org/en/latest/educators/concepts/exercise_tools/about_multi_select.html'
+- 'https://docs.openedx.org/en/latest/educators/how-tos/course_development/exercise_tools/add_multi_select.html'
+- 'https://docs.openedx.org/en/latest/educators/how-tos/course_development/exercise_tools/add_dropdown.html'
+- 'https://docs.openedx.org/en/latest/educators/how-tos/course_development/exercise_tools/manage_numerical_input_problem.html'
+- 'https://docs.openedx.org/en/latest/educators/how-tos/course_development/exercise_tools/add_text_input.html'
+- 'https://docs.openedx.org/en/latest/educators/how-tos/course_development/social_sharing.html'
+- 'https://docs.openedx.org/en/latest/educators/references/course_development/exercise_tools/guide_problem_types.html#advanced-problem-types'
+- 'https://docs.openedx.org/en/latest/educators/references/course_development/parent_child_components.html'
+- 'https://openai.com/api-data-privacy'
+- 'https://docs.openedx.org/en/latest/educators/how-tos/course_development/create_new_library.html'
+- 'https://bigbluebutton.org/privacy-policy/'
+- 'https://creativecommons.org/about'
+
+Note: as new external URLs are added to the codebase, more URLs will be wrapped with `getExternalLinkUrl` and this list may not always be up to date.
+
+How to Override External URLs
+-----------------------------
+
+To override external URLs, you can use the frontend platform's configuration system.
+This object should be added to the config object defined in the env.config.[js,jsx,ts,tsx], and must be named externalLinkUrlOverrides.
+
+1. **Environment Configuration**
+   Add the URL overrides to your environment configuration:
+
+   .. code-block:: javascript
+
+      const config = {
+        // Other config options...
+        externalLinkUrlOverrides: {
+          'https://www.edx.org/accessibility': 'https://your-custom-domain.com/accessibility',
+          // Add other URL overrides here
+        }
+      };
+
+Examples
+--------
+
+**Original URL:** Default community accessibility link
+**Override:** Your institution's accessibility policy page
+
+.. code-block:: javascript
+
+   // In your app configuration
+   getExternalLinkUrl('https://www.edx.org/accessibility')
+   // Returns: 'https://your-custom-domain.com/accessibility'
+   // Instead of the default Open edX community link
+
+Benefits
+--------
+
+- **Customization**: Institutions can point to their own resources
+- **Maintainability**: URLs can be changed without code modifications  
+- **Consistency**: Centralized URL management across the application
+- **Flexibility**: Different environments can have different external links