Story

As a plugin developer I want use the appLanguageApi as a simple mock solution, similar to other mocks from @backstage/test-utils.

This should simplify and streamline the unit test effort of plugins. It should allow us to use it like this:

<TestApiProvider
  apis={[
    [appLanguageApiRef, mockApis.appLanguage({ defaultLanguage: "en", availableLanguages: ["en", "fr" ] })],
  ]}
>

Background

1. https://github.com/redhat-developer/rhdh-plugins/blob/main/workspaces/adoption-insights/plugins/adoption-insights/src/components/CatalogEntities/__tests__/CatalogEntities.test.tsx#L22-L36
   #https://github.com/redhat-developer/rhdh-plugins/blob/main/workspaces/lightspeed/plugins/lightspeed/src/components/__tests__/LightspeedChat.test.tsx#L104-L124

Dependencies and Blockers

• No QE impact but helps with unit tests.
• No docs impact

Acceptance Criteria

• Upstream contribution might require additional unit tests and documentation
• The appLanguage mock might need some optional configuration like the default/initial language and the available languages.