[CMS] Translations returned by get_string are distorted in non-default locales when the string is coming from the default locale

[kvas]

Environment

CMS revision 1d0e9a76f62d, static generation or test server.

How to reproduce

See ​#148 in GitLab or follow these steps for a micro-scenario:

1. Set up a page that is a template containing the following code: {{ get_string('demo') }}
2. In the translation file for the default locale assign the following text to the translation string for "demo": <a href="http://foo.com/">Foo</a>.
3. In the translation file for another locale make sure that the translation for "demo" is absent.
4. Visit the page in another locale.

Observed behaviour

The HTML markup of the link in the translation string is quoted, the source of the page contains:

&lt;a href=&quot;http://foo.com/&quot;&gt;foo&lt;/a&gt;

instead of

<a href="http://foo.com/">Foo</a>

Expected behaviour

The HTML markup of the link should not be quoted (this is the behavior in the default locale, which is using the same string).

Note: the explanation of the reason for this bug can be found in ​#148. Look for crossed-out text.

[abpbot]

A commit referencing this issue has landed:
​Issue 7048 - Fix erroneous markup escaping in translation strings