[DPE-10625] select valid backup entry in restore integration test (#1840)

test_restore_on_new_cluster selected a backup ID from the list-backups
output by positional index (backups.split("\n")[-3]), assuming the last
two entries are always restore/timeline records. When the output
contains a different number of such entries, the selected line is
itself a timeline entry, which fails with "Cannot restore to the
timeline without restore-to-time parameter".

Parse the pipe-delimited output instead and select only lines whose
action column contains "backup" (full/differential/incremental),
and include action.results in the restore assertion message.

Backport of canonical/postgresql-k8s-operator#1552.

Assisted-by: Claude:claude-5-fable

Author: taurus-forever

tests/integration/test_backups_gcp.py

@@ -131,15 +131,28 @@ async def test_restore_on_new_cluster(
     ):
         with attempt:
             logger.info("restoring the backup")
-            # Last two entries are 'action: restore', that cannot be used without restore-to-time parameter
-            most_recent_real_backup = backups.split("\n")[-3]
-            backup_id = most_recent_real_backup.split()[0]
+            # The list-backups output contains real backup entries (action = "full backup",
+            # "differential backup", "incremental backup") as well as restore/timeline entries
+            # (action = "restore") that cannot be used without the restore-to-time parameter.
+            # Select only lines where the action column contains "backup" to avoid picking
+            # a timeline entry that would cause: "Cannot restore to the timeline without
+            # restore-to-time parameter".
+            real_backup_lines = [
+                line
+                for line in backups.splitlines()
+                for parts in [line.split("|")]
+                if len(parts) > 1 and "backup" in parts[1].lower()
+            ]
+            assert real_backup_lines, (
+                f"No valid backup entry found in list-backups output:\n{backups}"
+            )
+            backup_id = real_backup_lines[-1].split()[0]
             action = await ops_test.model.units.get(unit_name).run_action(
                 "restore", **{"backup-id": backup_id}
             )
             await action.wait()
             restore_status = action.results.get("restore-status")
-            assert restore_status, "restore hasn't succeeded"
+            assert restore_status, f"restore hasn't succeeded: {action.results}"
 
     # Wait for the restore to complete.
     async with ops_test.fast_forward():