Add JSON Output to List Command

[josecelano]

Overview

Add machine-readable JSON output format (--output-format json) to the list command. This enables automation workflows and AI agents to programmatically extract environment information (full names, states, providers, timestamps) without parsing human-readable text tables that may truncate long names.

Parent Epic: #348 - Add JSON output format support
Roadmap: Section 12.5
Specification: docs/issues/359-add-json-output-to-list-command.md

Goals

• Implement JSON output format for list command
• Preserve existing human-readable table output as default
• Enable automation to extract full environment names without truncation
• Follow the architecture pattern established in Add JSON Output to create Command #349, Add JSON output to provision command #352, Add JSON output to show command #355, and Add JSON output to run command #357

Rationale

Why JSON Output for List?

The table format truncates long environment names to fit the terminal width, making it difficult to:

• Parse environment names programmatically
• Disambiguate environments with long names
• Extract complete environment information for automation workflows

JSON output provides:

• Full environment names without truncation
• Structured data for easy parsing with jq or programming languages
• Complete state and timestamp information for each environment
• Failed environment details for error handling

Implementation Approach

Following the established Strategy Pattern from #349, #352, #355, and #357:

1. Create JsonView in src/presentation/views/commands/list/views/json_view.rs
2. Add #[derive(Serialize)] to EnvironmentList and EnvironmentSummary DTOs
3. Update ListCommandController to accept output_format parameter
4. Update router to pass output_format from ExecutionContext
5. Add comprehensive unit tests
6. Update user documentation with JSON examples and automation use cases

Example JSON Output

{
  "environments": [
    {
      "name": "production-high-availability-tracker",
      "state": "Running",
      "provider": "Hetzner",
      "created_at": "2026-02-14T16:45:00Z"
    },
    {
      "name": "staging-environment",
      "state": "Provisioned",
      "provider": "LXD",
      "created_at": "2026-02-10T09:15:00Z"
    }
  ],
  "total_count": 2,
  "failed_environments": [],
  "data_directory": "/path/to/project/data"
}

Automation Use Cases

# Extract all environment names
torrust-tracker-deployer list -o json | jq -r '.environments[].name'

# Filter by state
torrust-tracker-deployer list -o json | jq -r '.environments[] | select(.state == "Running") | .name'

# Count by provider
torrust-tracker-deployer list -o json | jq '.environments | group_by(.provider) | map({provider: .[0].provider, count: length})'

Success Criteria

• ✅ JSON output implemented following Strategy Pattern
• ✅ Full environment names provided without truncation
• ✅ All tests passing (unit + integration)
• ✅ All linters passing
• ✅ Documentation updated with JSON examples and automation use cases
• ✅ Backward compatible (text output unchanged)

Related Issues

• Part of EPIC EPIC: Add JSON output format support #348 (Phase 1: JSON Output for High-Value Commands)
• Task 12.5 in project roadmap
• Follows pattern from:
  • Add JSON Output to create Command #349 (create command) ✅
  • Add JSON output to provision command #352 (provision command) ✅
  • Add JSON output to show command #355 (show command) ✅
  • Add JSON output to run command #357 (run command) ✅