Setup new backend

[erikasv]

🛠️ Changes

• create endpoints to get data and layer for a given metric (metric was the term defined by Cesar for all "cifras e indicadores" from the search module)
• Read dotenv and disable swagger in production
• Document some of the parameters, the validation for the polygon is more complex, so I'll include it in another issue

📝 Associated issues

187

🤔 Considerations

There is a problem with the length of the line in docstrings, black won't trim them and flake8 will complain... we'll have to discuss other tools or alternatives for this, because the only available option for the moment is to exclude one by one (docstring)