Summary

This PR implements configurable date and time formatting support in Nextflow to make timestamps consistent and ISO-compliant across all outputs.

Features Added

• Configurable Date Format: New NXF_DATE_FORMAT environment variable allows users to customize date formatting
• ISO Format Support: Set NXF_DATE_FORMAT=iso for ISO 8601 format with timezone information (2016-08-11T09:40:20+02:00)
• Default Format Updated: Changed to dd-MMM-yyyy HH:mm:ss (includes seconds for better precision)
• Universal Template Support: All notification templates now use the configurable format:
  • Email notifications (HTML and text)
  • HTML execution reports
  • ANSI console output

Technical Implementation

• Enhanced SysHelper: Added support for OffsetDateTime objects commonly used in workflow metadata
• Template Binding: Fixed template engines to properly access SysHelper formatting methods
• Backward Compatibility: Existing behavior preserved - only adds new functionality

Usage Examples

# Default format (dd-MMM-yyyy HH:mm:ss)
nextflow run workflow.nf
# Output: "11-Aug-2016 09:40:20"

# ISO format with timezone
export NXF_DATE_FORMAT=iso
nextflow run workflow.nf  
# Output: "2016-08-11T09:40:20+02:00"

# Custom format
export NXF_DATE_FORMAT="yyyy-MM-dd HH:mm"
nextflow run workflow.nf
# Output: "2016-08-11 09:40"

Documentation Added

• Environment Variables Reference: Added NXF_DATE_FORMAT documentation with version 25.07.0-edge
• Migration Guide: Added feature description to 25.10 migration guide with usage examples
• Version Information: Properly documented as available since version 25.07.0-edge

Files Modified

• SysHelper.groovy - Core formatting logic with environment variable support
• notification.html & notification.txt - Email template updates
• ReportTemplate.html - HTML report template updates
• AnsiLogObserver.groovy - Console output formatting
• WorkflowNotifier.groovy & ReportObserver.groovy - Template binding fixes
• docs/reference/env-vars.md - Environment variable documentation
• docs/migrations/25-10.md - Feature documentation and examples
• Comprehensive test coverage added and updated

Testing

• ✅ All existing tests pass
• ✅ New test coverage for OffsetDateTime support
• ✅ Template rendering tests for all notification types
• ✅ Environment variable configuration tests
• ✅ ISO format and timezone handling tests

This addresses the inconsistency issues mentioned in #4754 by providing a centralized, configurable date formatting system.

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