feat: add support for multilingual UI

[staceybeard]

By submitting this merge request, I confirm the following:

• The merge request title follows the conventional commits convention (see Backend project's README.md)
  • feat: minor app version will be incremented.
  • fix, deps, perf: patch app version will be incremented.
  • chore, ci, etc.: app version will not be incremented.
  • See semantic-release/commit-analyzer
    for complete set of rules.

Changes

Updated code across the app to support a truly multilingual UI.

While angular-translate was already set up to facilitate adding more languages, the app's controllers and views still expected data to be provided in either English or French. This meant that setting the app to a new language would break the majority of the data display. The PR linked below moves the responsibility to the listener to provide translated strings and data, with a fallback language when the requested language isn't available. This allows the app to receive and display data in any language, and allows the user to set the UI to a language other than English or French.

The following example describes the most common change required for a multilingual UI. Suppose a piece of data has a description; the data would come from the listener with fields Description_EN and Description_FR. The app view would then display Description_${language}. However, with the app in Spanish (for example), the view would be trying to access Description_ES, which doesn't exist. To fix this problem, the code was changed to expect just a Description, already translated by the listener either in the correct language or a fallback language.

Extra changes:

• Deleted unused src/views/personal/documents/pdf-view.html. Then renamed pdf-view.directive.css to pdf-viewer.directive.css for clarity.
• Installed @babel/plugin-proposal-throw-expressions to allow the syntax return data || throw error; (used in dynamicContentService.js when a link is missing in the chosen language and in the fallback language).

Dependencies

• Listener: feat: add support for multilingual app UI opal-listener#581

Screenshots

The following languages are provided as an example.

[mschoettle]

Great work!

[staceybeard]

Great work!

Thanks @mschoettle!