Add groupName property support for AWS::Scheduler::Schedule Event in Lambda Functions

Description

This PR adds support for the groupName property in the AWS::Scheduler::Schedule resource when using the method: scheduler option for schedule events. This allows users to organize their schedules into logical groups, making it easier to manage related schedules together.

Changes

1. Added the groupName property to the schema definition with appropriate validation rules
2. Added validation to ensure groupName is only used with the scheduler method
3. Modified the resource creation logic to include the GroupName property in the AWS::Scheduler::Schedule resource
4. Added tests to verify the functionality of the groupName property
5. Updated documentation to include information about the groupName property

Example Usage

functions:
  foo:
    handler: foo.handler
    events:
      - schedule:
          method: scheduler
          rate: rate(15 minutes)
          groupName: my-schedule-group
          name: my-scheduled-event
          description: 'Scheduled event with group'
          input: '{"key": "value"}'

Testing

• Added unit tests to verify that the groupName property is correctly set in the CloudFormation resources
• Added a test to verify that an error is thrown when groupName is used with method: eventBus

Checklist

• I have tested these changes locally
• I have updated the documentation accordingly
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes