Improve Gladys Plus integration

[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 your changes modify the API (REST or Node.js), did you modify the documentation? (Documentation is based on comments in code)

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

Description of change

Please provide a description of the change here. It's always best with screenshots, so don't hesitate to add some!

[codecov]

Codecov Report

Merging #535 into master will decrease coverage by 0.12%.
The diff coverage is 69.84%.

@@            Coverage Diff             @@
##           master     #535      +/-   ##
==========================================
- Coverage   91.39%   91.27%   -0.13%     
==========================================
  Files         342      345       +3     
  Lines        3882     3941      +59     
==========================================
+ Hits         3548     3597      +49     
- Misses        334      344      +10

Flag	Coverage Δ
#server	91.27% <69.84%> (-0.13%)	⬇️

Impacted Files	Coverage Δ
server/utils/constants.js	100% <ø> (ø)	⬆️
server/api/routes.js	97.95% <ø> (ø)	⬆️
server/lib/gateway/gateway.init.js	25.8% <0%> (-27.53%)	⬇️
server/api/controllers/gateway.controller.js	60% <100%> (+3.47%)	⬆️
server/lib/variable/index.js	100% <100%> (ø)	⬆️
server/lib/gateway/index.js	100% <100%> (ø)	⬆️
server/lib/variable/variable.destroy.js	100% <100%> (ø)
server/lib/gateway/gateway.loginTwoFactor.js	100% <100%> (ø)	⬆️
server/api/controllers/variable.controller.js	83.33% <100%> (+54.76%)	⬆️
server/lib/gateway/gateway.handleNewMessage.js	86.36% <100%> (ø)	⬆️
... and 7 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a2dddd3...2f65a49. Read the comment docs.