Add the ability to send a new device feature state in Gladys Plus Open API

[Pierre-Gilles]

Pull Request check-list

To ensure your Pull Request can be accepted as fast as possible, make sure to review and check all of these items:

• If your changes affects code, did your write the tests?
• Are tests passing? (npm test on both front/server)
• Is the linter passing? (npm run eslint on both front/server)
• Did you run prettier? (npm run prettier on both front/server)
• If you are adding a new features/services, did you run integration comparator? (npm run compare-translations on front)
• If your changes modify the API (REST or Node.js), did you modify the API documentation? (Documentation is based on comments in code)
• If you are adding a new features/services which needs explanation, did you modify the user documentation? See the GitHub repo and the website.
• Did you add fake requests data for the demo mode (front/src/config/demo.json) so that the demo website is working without a backend? (if needed) See https://demo.gladysassistant.com.

NOTE: these things are not required to open a PR and can be done afterwards / while the PR is open.

Description of change

Little demo:

[codecov]

Codecov Report

Merging #1184 (75569d2) into master (0f4f052) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1184      +/-   ##
==========================================
+ Coverage   96.42%   96.44%   +0.02%     
==========================================
  Files         643      643              
  Lines        8193     8196       +3     
==========================================
+ Hits         7900     7905       +5     
+ Misses        293      291       -2     

Impacted Files	Coverage Δ
server/lib/gateway/gateway.handleNewMessage.js	90.32% <100.00%> (+8.17%)	⬆️

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