Enhance DailyAutomaticBackupStartTime with defaults, parsing, and validation fixes

[Imadnajam]

Reason for this change

• Fixes incorrect validation message for hour range (previously showed "0-24" instead of "0-23")
• Adds support for parsing time strings in "HH:MM" format
• Implements sensible defaults (22:00 UTC) for backup start time
• Improves developer experience with better input validation and formatting

Description of changes

1. Core Changes:

   • Added static fromString() method to parse "HH:MM" formatted time strings
   • Implemented default values (hour: 22, minute: 0) when no props are provided
   • Updated validation logic with correct hour range (0-23)
   • Improved string padding using padStart() instead of manual concatenation

2. Design Decisions:

   • Maintained backward compatibility with existing constructor
   • Chose 22:00 UTC (default) as it's typically off-peak for most regions
   • Implemented strict validation for both constructor and string parsing
   • Used regex pattern matching for string input validation

3. AWS Use Cases Enabled:

   • Simplifies backup scheduling for:
     • Amazon RDS automated backups
     • Amazon EFS backup configurations
     • AWS Backup plan schedules
   • Provides reusable time validation for:
     • CloudFormation custom resources
     • Lambda-backed custom constructs

Describe any new or updated permissions being added

No new permissions are required as this change only affects client-side validation and formatting logic.

Description of how you validated changes

1. Unit Testing:

   • Added 15 new test cases covering:
     • Default value behavior
     • Valid/invalid time inputs
     • String parsing functionality
     • Edge cases (00:00, 23:59)
     • Error conditions

2. Manual Validation:

   • Verified integration with existing CDK constructs
   • Tested with AWS Backup plan creation
   • Confirmed backward compatibility

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AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: 9a07df3
• Result: FAILED
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