chore(stepfunction-tasks): eventbridge aws. event source prefix check is more strict than it should be (#30237)

1. fix the event source validation
2. move the validation from renderEntries() to validateEntries() 
3. add unit tests

### Issue # (if applicable)

Closes #30191

### Reason for this change



### Description of changes



### Description of how you validated changes



### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: pahud

Diff for: packages/aws-cdk-lib/aws-stepfunctions-tasks/lib/eventbridge/put-events.ts

@@ -132,23 +132,23 @@ export class EventBridgePutEvents extends sfn.TaskStateBase {
   }
 
   private renderEntries(): Object[] {
+    // we should have validated all entries in validateEntries()
     return this.props.entries.map(entry => {
-      if (entry.source?.startsWith('aws')) {
-        throw new Error('Event source cannot start with "aws."');
-      } else {
-        return {
-          Detail: entry.detail?.value,
-          DetailType: entry.detailType,
-          EventBusName: entry.eventBus?.eventBusArn,
-          Source: entry.source,
-        };
-      }
+      return {
+        Detail: entry.detail?.value,
+        DetailType: entry.detailType,
+        EventBusName: entry.eventBus?.eventBusArn,
+        Source: entry.source,
+      };
     });
   }
 
   private validateEntries(): void {
     if (this.props.entries.length <= 0) {
       throw new Error('Value for property `entries` must be a non-empty array.');
     }
+    if (this.props.entries.some(e => e.source.startsWith('aws.'))) {
+      throw new Error('Event source cannot start with "aws."');
+    }
   }
 }

Diff for: packages/aws-cdk-lib/aws-stepfunctions-tasks/test/eventbridge/put-events.test.ts

@@ -161,6 +161,30 @@ describe('Put Events', () => {
     }).toThrowError('Unsupported service integration pattern');
   });
 
+  test('event source cannot start with "aws."', () => {
+    expect(() => {
+      new EventBridgePutEvents(stack, 'PutEvents', {
+        entries: [{
+          detail: sfn.TaskInput.fromText('MyDetail'),
+          detailType: 'MyDetailType',
+          source: 'aws.source',
+        }],
+      });
+    }).toThrow(/Event source cannot start with "aws."/);
+  });
+
+  test('event source can start with "aws" without trailing dot', () => {
+    expect(() => {
+      new EventBridgePutEvents(stack, 'PutEvents', {
+        entries: [{
+          detail: sfn.TaskInput.fromText('MyDetail'),
+          detailType: 'MyDetailType',
+          source: 'awssource',
+        }],
+      });
+    }).not.toThrow(/Event source cannot start with "aws."/);
+  });
+
   test('provided EventBus', () => {
     // GIVEN
     const eventBus = new events.EventBus(stack, 'EventBus');