Is this feature request related to a new rule or cfn-lint capabilities?

New capability

Describe the feature you'd like to request

Currently cfn-lint is unable to recognize if the "StartAt" state is unreachable. The following CloudFormation Template will cause a CloudFormation error:

AWSTemplateFormatVersion: 2010-09-09
Description: Test

Resources:
  StepFunctionRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Statement:
          - Effect: Allow
            Principal:
              Service: states.amazonaws.com
            Action: sts:AssumeRole

  StateMachine:
    Type: AWS::StepFunctions::StateMachine
    Properties:
      RoleArn: !GetAtt StepFunctionRole.Arn
      Definition:
        StartAt: Not sure # <-------------- State doesn't exist
        States:
          Pass One:
            Type: Pass
            Next: Success
          Success:
            Type: Succeed

CloudFormation error:

Resource handler returned message:
"Invalid State Machine Definition:
'MISSING_TRANSITION_TARGET: Missing 'Next' target: Not sure at /StartAt,
MISSING_TRANSITION_TARGET: State "Pass One" is not reachable. at /States/Pass One'
(Service: Sfn, Status Code: 400, Request ID: 4...8) (SDK Attempt Count: 1)"
(RequestToken: 0...9, HandlerErrorCode: InvalidRequest)

It would be great if cfn-lint could give an error on these.

Describe the solution you'd like

A new/updated rule to notify the user of this error.

Additional context

No response

Is this something that you'd be interested in working on?

• 👋 I may be able to implement this feature request

Would this feature include a breaking change?

• ⚠️ This feature might incur a breaking change