Fix Postgre connection string

Docker/docker-compose.yaml

@@ -9,7 +9,7 @@ services:
       - "8080:8080"
     environment:
       - DOTNET_RUNNING_IN_CONTAINER=true
-      - ConnectionStrings__DefaultConnection=Host=postgresdb;Port=5432;Database=flightlog;Username=postgres;Password=secret
+      - NpgsqlConnectionString=Host=postgresdb;Port=5432;Database=flightlog;Username=postgres;Password=secret
     depends_on:
       postgresdb:
         condition: service_healthy