Fix test DB connection - disable SSL

PostgreSQL in Docker requires SSL but tests weren't configured for it.
Adding ?sslmode=disable to the connection string fixes TLS errors.

backend/testutils/testdb/testdb.go

@@ -14,7 +14,7 @@ import (
 	"github.com/jackc/pgx/v5/pgxpool"
 )
 
-const defaultTestDSN = "postgres://myuser:mypassword@localhost:5432/crussell_test"
+const defaultTestDSN = "postgres://myuser:mypassword@localhost:5432/crussell_test?sslmode=disable"
 
 func Pool(t *testing.T) *pgxpool.Pool {
 	t.Helper()