Avoid password auth in odata_basics.ipynb

[soxofaan]

odata_basics.ipynb has this snippet to do auth:

# Provide CDSE account credentials - replace with your own data
import os

username = os.environ["CDSE_USERNAME"]
password = os.environ["CDSE_PASSWORD"]

# Get authentication token
import certifi

auth_server_url = "https://identity.dataspace.copernicus.eu/auth/realms/CDSE/protocol/openid-connect/token"
data = {
    "client_id": "cdse-public",
    "grant_type": "password",
    "username": username,
    "password": password,
}

We should avoid promoting password grant like this.
And, while os.environ is used, it is a slippery slope for users to just put their main CDSE password directly in source code.