In Webapps, HTML lang attribute value is not dynamically set based on the available and requested languages

Environment (Required on creation):

Camunda Automation Platform 7.17.0

Description (Required on creation; please attach any relevant screenshots, stacktraces, log files, etc. to the ticket):

The browser (e.g., Google Chrome) shows a popup that offers to translate the Camunda Webapp, although the right localization of the Webapp is already shown.

translation-offer-popup.png

Steps to reproduce (Required on creation):

1. Change the language in your browser to any language other than english; make sure english is not defined as the fallback language
2. Configure any Camunda Webapp to use the previously defined language; make sure english is not defined as a fallback language [1]
3. Open any Camunda Webapp

Observed Behavior (Required on creation):

Even though the Camunda Webapp is correctly translated, the translation offer popup is shown.

Expected behavior (Required on creation):

The translation offer popup is only shown when the requested browser language and the language of the Camunda Webapp differ.

Root Cause (Required on prioritization):

The HTML lang attribute value is hardcoded to en [2].

Solution Ideas (Optional):

1. The user changes the HTML lang attribute value in the index.html to the preferred language
   • Cons:
     • Solution is not reactive to the respective language requested by the client
2. HTML lang attribute value is changed dynamically client-side (frontend)
   • Cons:
     • This only solves the problem for the screenreader but not for the translation offer popup since it doesn't react to client-side changes
3. HTML lang attribute is dynamically served server-side (backend) based on the request header Accept-Language
   • Cons:
     • Effort is higher
     • Under some circumstances, the problem still exists:
       • Our localization feature [1] is implemented on the client-side (frontend), which means our backend is not aware if the language the browser requests is actually supported
       • The server might set the language to an unsupported language, but the Webapp is actually translated to a different language
       • As a result, the browser offers to translate from a wrong source language

Hints (optional):

-

Original Ticket Description

The lang attribute of the main HTML tag is always set to "en" even if a different locale is set (fr in my case).

Consequently, some browsers ask users to translate the page, and if the user says yes, some words can be changed.

[1] https://docs.camunda.org/manual/7.17/webapps/cockpit/extend/configuration/#localization
[2] https://github.com/camunda/camunda-bpm-platform/blob/bf97f3/webapps/ui/tasklist/client/index.html#L2