feat(new sink): add Apache Doris sink support

[bingquanzhao]

Summary

This PR introduces a new Apache Doris sink for Vector, enabling users to send log data directly to Apache Doris databases using the Stream Load API. The implementation includes:

• Complete Doris sink implementation with Stream Load API integration
• Comprehensive configuration options (endpoints, authentication, batching, custom headers)
• Full documentation generation using CUE
• Health check functionality with proper error handling
• Support for Doris-specific Stream Load parameters via custom HTTP headers

Apache Doris is a modern MPP analytical database that provides sub-second query response times on large datasets, making it ideal for real-time data warehouses and log analysis scenarios.

Change Type

• New feature
• Bug fix
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

How did you test this PR?

Local Testing

1. Unit Tests: All unit tests pass with cargo test
2. Configuration Validation: Verified config parsing with vector validate
3. Documentation Generation: Successfully generated docs with make generate-component-docs
4. CUE Validation: All CUE files pass format and validation checks
5. Changelog Validation: Changelog fragment passes validation with ./scripts/check_changelog_fragments.sh

Test Configuration Used

sources:
  demo:
    type: demo_logs
    format: json
    interval: 1

sinks:
  doris:
    type: doris
    inputs: ["demo"]
    
    # Target configuration
    endpoints: 
      - "http://doris-fe1:8030"
      - "http://doris-fe2:8030"
    database: "analytics_db"
    table: "user_events"
    
    # Authentication configuration
    auth:
      strategy: basic
      user: "admin"
      password: "admin123"
    
    # Batch configuration
    batch:
      max_events: 100000        # Maximum events per batch
      timeout_secs: 30          # Batch timeout in seconds
      max_bytes: 1073741824     # Maximum bytes per batch (1GB)
    
    # Custom HTTP headers for Doris Stream Load
    headers:
      format: "json"
      strip_outer_array: "false"
      read_json_by_line: "true"
    
    # Additional configuration
    label_prefix: "vector"
    log_request: true
    log_progress_interval: 10
    buffer_bound: 1

Environment Setup

• Tested configuration validation against Vector's validation system
• Verified health check functionality (attempts connection to configured endpoints)
• All documentation generation and validation checks pass
• CUE v0.7.0 used for documentation generation

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

Notes

Implementation Details

• Stream Load API: Uses Doris's native Stream Load API for optimal performance and compatibility
• Authentication: Supports basic authentication with username/password
• Batching: Configurable batching with event count, byte size, and timeout limits
• Custom Headers: Support for Doris-specific Stream Load parameters via HTTP headers including:
  • format: Data format specification (json, csv, etc.)
  • read_json_by_line: JSON line-by-line reading mode
  • strip_outer_array: Array handling configuration
  • columns: Column mapping specification
• Error Handling: Comprehensive error handling with configurable retry logic
• Health Checks: Validates connectivity and basic authentication
• Rate Limiting: Built-in rate limiting and adaptive concurrency control

Documentation

• Added complete CUE documentation for the sink configuration
• Generated reference documentation automatically using Vector's documentation system
• Updated service definitions and URL references
• All documentation validation checks pass (CI=true make check-docs)

Dependencies

• No new external dependencies added
• Uses existing Vector HTTP client infrastructure
• Leverages standard Vector authentication, batching, and request frameworks
• Follows Vector's established patterns for sink implementation

Code Quality

• All code formatted with cargo fmt
• Follows Vector's coding standards and patterns
• Proper error handling and logging throughout
• Comprehensive configuration validation

Testing Strategy

• Configuration validation ensures all options are properly parsed
• Health check functionality verified through connection attempts
• Documentation generation confirms all metadata is correctly defined
• Follows Vector's established testing patterns for sinks

References

• Apache Doris Stream Load Documentation: https://doris.apache.org/docs/data-operate/import/import-way/stream-load-manual
• Apache Doris Official Website: https://doris.apache.org
• Vector Sink Development Guidelines: https://vector.dev/docs/reference/configuration/sinks/

[bits-bot]

All committers have signed the CLA.

[drichards-87]

Created Jira card for Docs Team review.

[maycmlee]

Some small suggestions