feat(backup): S3 target supports optional endpoint_url (e.g. for Backblaze)

[tsgoff]

The S3 backup target can be used with any S3-compatible endpoint by optionally providing an endpoint_url parameter. This enables usage with services like Backblaze B2 Cloud Storage.

General information
This change extends the S3 backup target to support any S3-compatible storage by allowing an optional endpoint URL to be specified. This enables direct backup to providers like Backblaze B2 Cloud Storage, which offer an S3-compatible API.

Proposed changes
The S3 backup target now accepts an optional parameter.
If provided, this endpoint is used for all S3 operations, making it possible to use non-AWS S3-compatible storage (e.g., Backblaze B2).
The default behavior for AWS S3 remains unchanged if no endpoint is specified.
Expected behavior:
Users can configure the backup target to use any S3-compatible storage by specifying the appropriate endpoint URL.

Observed behavior before the change:
Only AWS S3 could be used, as the endpoint was not configurable.

How this patch changes the current behavior:
The patch adds flexibility by allowing the endpoint to be set, enabling support for additional S3-compatible providers.

[github-actions]

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[tsgoff]

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[kain88-de]

Hi. Thanks this is a good addition. The endpoint setting is not visible from the UI yet. With this change it will be added.

cmk/gui/backup/handler.py --- Python
1424 1424                     ],
1425 1425                 ),
1426 1426             ),
.... 1427             "endpoint_url": DictElement(
.... 1428                 required=False,
.... 1429                 parameter_form=String(
.... 1430                     title=Title("Endpoint URL (optional)"),
.... 1431                     help_text=Help(
.... 1432                         "Custom endpoint URL for S3-compatible storage services (e.g., Backblaze B2). "
.... 1433                         "Leave empty to use the default AWS S3 endpoint."
.... 1434                     ),
.... 1435                 ),
.... 1436             ),
1427 1437         }
1428 1438
1429 1439

Can you have a check please that with this you can set the endpoint url from the UI. Thank you.