Improve models.py documentation, small DATABASE_URL check

backend/linkpulse/models.py

@@ -1,14 +1,32 @@
-from peewee import Model, CharField, DateTimeField, IntegerField
+"""models.py
+This module defines the database models for the LinkPulse backend.
+It also provides a base model with database connection details.
+"""
+
+from os import getenv
+
+import structlog
+from peewee import CharField, DateTimeField, IntegerField, Model
 from playhouse.db_url import connect
-from os import environ
+
+logger = structlog.get_logger()
+
+
+# I can't pollute the class definition with these lines, so I'll move them to a separate function.
+def __get_database_url():
+    url = getenv("DATABASE_URL")
+    if url is None or url.strip() == "":
+        raise ValueError("DATABASE_URL is not set")
+    return url
 
 
 class BaseModel(Model):
     class Meta:
-        database = connect(url=environ.get("DATABASE_URL"))
+        # accessed via `BaseModel._meta.database`
+        database = connect(url=__get_database_url())
 
 
 class IPAddress(BaseModel):
     ip = CharField(primary_key=True)
-    last_seen = DateTimeField()
+    last_seen = DateTimeField()  # timezone naive
     count = IntegerField(default=0)