Load Agama translations

[lslezak]

Problem

• The Agama translations are not loaded from the server
• Changing the language has no effect although the translations are present on the server

Solution

• Load the po.js file with translations

Notes

• Cockpit handles loading of the right translations on the server side, see the note in the HTML code
• The HTML comment is currently present also in the built production code, later I'll reconfigure webpack to also minify HTML files
• The defer attribute is needed because the JS modules (index.js) are deferred by default. We need to defer also loading the localization code otherwise calling cockpit.locale() inside po.js would fail because it would not be defined yet. The cockpit.js file is bundled in the index.js file so that file needs to be loaded before the translations.

Testing

• Tested manually
• For switching the language use the original Cockpit language selector
  • Change the URL to point to the /cockpit/@localhost/shell/index.html path
  • This displays the full Cockpit web UI
  • Use the Session menu in the top right corner, select the Display language option
  • In the popup list select čeština (Czech)
  • Then go back to Agama (either revert the URL path to simple / or click the Agama label in the left side bar
• To display a Czech translation use the option menu (the hamburger icon in the top right corner) and select Diagnostic tools -> Show Log. So far there are just few translations to test, see the web/po/cs.po file.
• The displayed popup with YaST logs contains Zavřít translation for the Close button

Screenshots

The "Close" button with the Czech translation activated

[coveralls]

coverage: 72.051%. remained the same when pulling a89b700 on load_translations into 93aaa88 on master.

[mvidner]

For missing translations it returns an empty string.

Does this mean that if I miss to translate some strings, there will be empty texts?

Suggested change

	the HTTP header. For missing translations it returns an empty string.
	the HTTP header. For missing translations it returns an empty script.