Add hawkBit firmware management extension

[dominiquekleeven]

Closes #33

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Adds a hawkBit firmware extension that connects OpenRemote Manager to the hawkBit Management API, exposes firmware management endpoints, and syncs selected OpenRemote assets as hawkBit targets.

Core Functionality

• Registers firmware meta items for marking assets as firmware targets (FIRMWARE_TARGET) and syncing selected attributes as hawkBit metadata (FIRMWARE_METADATA).
  • FIRMWARE_TARGET causes the asset to be synced as a target to hawkBit.
  • FIRMWARE_METADATA causes the attribute and its value to be synced as metadata to the target within hawkBit. This enables hawkBit to use attribute-aware target filters for grouping purposes.
• Creates, updates, and deletes hawkBit targets in response to OpenRemote asset events.
• Updates OpenRemote firmware target info attributes with hawkBit controllerId and securityToken.
• Proxies firmware management endpoints for targets, software modules, distribution sets, target filters, and rollouts.
• Adds OpenRemote read/write admin authorization and configured-realm access checks around firmware endpoints.
• Adds artifact upload support for hawkBit software modules. (required a bit of a workaround, but streams the uploaded file to the hawkBit endpoint).

Core Files

• HawkbitFirmwareService.java: Starts the integration, configures the hawkBit client, registers API resources, and handles asset/attribute sync.
• HawkbitResponseProxy.java: Copies hawkBit responses back through OpenRemote while preserving status, body, and media type.
• manager/hawkbit/*Client.java: RESTEasy clients for hawkBit Management API resources.
• manager/resource/*ResourceImpl.java: OpenRemote API resource implementations that authorize requests and proxy them to hawkBit.
• model/resource/*Resource.java: Public OpenRemote firmware endpoint definitions and role requirements.
• FirmwareMetaItemType.java: Defines firmwareTarget and firmwareMetadata meta items.
• FirmwareModelProvider.java: Registers firmware meta items with the OpenRemote model.
• README.md: Documents setup, limitations, API coverage, deployment examples, and proxy configuration.

Caveats

• The integration is currently limited to a single OpenRemote realm configured by HAWKBIT_REALM.
• This extension is intended to be used with the companion hawkBit/OpenRemote management UI service: https://github.com/openremote/service-hawkbit-ui

Testing

• Added mock based testing for checking whether asset events / attribute events trigger the appropriate 'client' call, e.g. sync behaviour.
• Added simple tests for the proxy behaviour.

Notes

• The large changed file count and addition count is mostly caused by license headers + model interfaces. The actual logic and behaviour is fairly minimal in terms of complexity/LoC.
• Not all hawkBit management API endpoints are integrated, only those who are deemed necessary to enable basic firmware/OTA management.

[dominiquekleeven]

Would be nice to get this merged fairly quickly as I want to deploy the extension to staging for a custom project. Happy to go through the additions/changes if needed.