Introduce setting to increase max number fields

[lakridserne]

No description provided.

[what-the-diff]

PR Summary

• Introduction of new environment variable
  We've introduced a new environment variable, DATA_UPLOAD_MAX_NUMBER_FIELDS, which has been set to 10240. This is referenced in the .env.example file.

• Enhancements in 'settings.py' file
  We've improved the settings.py file to now read the DATA_UPLOAD_MAX_NUMBER_FIELDS environment variable and converts it into an integer. This allows for smoother and more efficient data management based on the preset upper limit.

[rasmusselsmark]

Kristoffer sætter variabel på staging+prd