Add NETCONF Support to IOS‑XR Terraform Provider

[hayibrah]

Overview

This PR introduces full NETCONF protocol support as an alternative to gNMI, enabling configuration management of IOS‑XR devices using NETCONF with improved reliability, flexibility, and performance.

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Key Features

NETCONF Support

• NETCONF 1.0/1.1 via go-netconf
• Candidate + running datastore workflows
• Automatic capability detection
• Subtree filter generation for IOS‑XR

Connection Management

• Optional connection reuse (default: enabled)
• Smart locking: concurrent reads, serialized writes
• Health checks, retries, reconnection logic
• Capability caching

NETCONF Operations

• Enhanced EditConfig with ignore‑missing and “no changes” handling
• GetConfig with timeout + retry
• Candidate and running datastore commit flows

Error Handling & Logging

• Detailed NETCONF error extraction
• Graceful handling of common conditions
• Structured + debug XML logging

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Benefits

• Faster operations via connection reuse
• More resilient sessions with retries + health checks
• Works with both candidate and non‑candidate devices
• Backward‑compatible with existing gNMI workflows

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Example Usage

provider "iosxr" {
  host             = "10.1.1.1:830"
  username         = "cisco"
  password         = "cisco123"
  protocol         = "netconf"
  reuse_connection = true
}

resource "iosxr_hostname" "example" {
  hostname = "router-1"
}