Add option_labels to questions for stable identifiers and translated labels

[mvidner]

• https://trello.com/c/GdxTSJpj/5205-3-sles160-use-identifiers-for-question-values

Problem

Agama questions have two attributes to define the possible answers:

• options: possible options the user can choose from.
• default_option: default option. This option is used by the web UI to decide which button to set as the default.

The problem is that, if you try to load an answers file, you need to make sure that Agama and your profile are in the same language. So instead of using translated values, we should use some kind of identifiers.

Solution

Where the old code had an options array, add also an option_labels array. The options will be untranslated IDs, the labels are translated and displayed to the user.

TODO:

• add translation markers N_("text") to the actual answers

Testing

• Some unit tests adjusted
• TODO: manual tests

How to test manually:

1. run ./testing-using-container.sh
2. zypper in -y glibc-locale
3. systemctl restart agama.service
4. open a browser at https://localhost:10443/
5. select French as the installer UI language
6. select a product (MicroOS)
7. cd /checkout # in the container again
8. agama config generate file://$(pwd)/service/test/fixtures/profiles/cloned.xml &
9. see a question in the browser
10. ...

Screenshots

TODO, make one

Documentation

Remember to look at it from the user's perspective. Yes you have made the compiler happy.
But will the humans even know about your contribution? Sometimes they cannot miss it,
other times they need advertisement and explanation.

Look for relevant sections and adjust:

• The description parts of the JSON schema
• Is the CLI affected? See cli.md for a complete overview,
  change the /// comments (rust doc)
  and update the .md with cargo xtask markdown
• https://agama-project.github.io/ (source)
• Run: git ls-files '*.md'

[coveralls]

coverage: 64.255% (-11.9%) from 76.149%
when pulling e96f941 on question-ids-and-labels
into fe93696 on master.