Fix mage conditional

Use data_host instead of target_hostname, because target_hostname is not available to the container.

geomagio/api/db/database.py

@@ -14,11 +14,11 @@ class Tables(str, Enum):
 
 
 database_url = os.getenv("DATABASE_URL", "sqlite:///./api_database.db")
-hostname = os.getenv("TARGET_HOSTNAME")
+data_host = os.getenv("DATA_HOST")
 
 try:
     engine = create_engine(database_url)
 except Exception as e:
     print("error creating engine:", e)
-    if "mage" in hostname:
+    if "mage" in data_host:
         pass