feat: add SolarWinds provider for pulling alerts via SWIS API

[vasquezmyguy-collab]

SolarWinds Provider Implementation

/claim #3526

Summary

This PR adds a new SolarWinds provider to Keep that polls the SolarWinds SWIS REST API for alerts.

Features

• Polling Provider: Pulls active and recently resolved alerts from SolarWinds NPM/NCM via SWQL queries
• Webhook Support: Includes _format_alert method for push/webhook alerts from SolarWinds
• Authentication: Supports hostname, username, password with configurable port (default 17778) and HTTPS toggle (default True)
• Severity Mapping: Maps SolarWinds severity levels (Critical, Warning, Informational, etc.) to Keep AlertSeverity
• Status Mapping: Maps SolarWinds alert states (Active, Acknowledged, Resolved, Cleared) to Keep AlertStatus
• Node Details: Enriches alerts with node information (hostname, IP, node URL)
• Mock Data: Includes sample alert data for testing and documentation

Files Added

• keep/providers/solarwinds_provider/__init__.py
• keep/providers/solarwinds_provider/solarwinds_provider.py
• keep/providers/solarwinds_provider/alerts_mock.py

Testing

• Provider follows the same pattern as other polling providers (e.g., Centreon, Site24x7)
• Validated authentication via SWQL query against Orion.AlertActive
• Tested SWQL queries for both active and resolved alerts

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