Event Bridge example with L2 Rule construct instead of L1 Cfn

### Environment information

```plain text
npx ampx info
System:
OS: macOS 14
CPU: (8) arm64 Apple M2
Binaries:
Node: 20.15.0 - ~/.n/bin/node
Yarn: 4.3.1 - ~/.n/bin/yarn
npm: 10.7.0 - ~/.n/bin/npm
pnpm: undefined - undefined
NPM Packages:
@aws-amplify/backend: 1.0.4
@aws-amplify/backend-cli: 1.1.0
aws-amplify: 6.3.8
aws-cdk: 2.147.2
aws-cdk-lib: 2.147.2
typescript: 5.5.2
AWS environment variables:
AWS_STS_REGIONAL_ENDPOINTS = regional
AWS_NODEJS_CONNECTION_REUSE_ENABLED = 1
AWS_SDK_LOAD_CONFIG = 1
No CDK environment variables
```

### Description

Regarding EventBridge example for data sources

https://docs.amplify.aws/react/build-a-backend/data/custom-business-logic/connect-eventbridge-datasource/

I'm trying to setup this example with L2 construct Rule (https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_events.Rule.html)

This is the class, where api is `backend.data.resources.graphqlApi`

```
export class FileSearchEventBus extends Construct {
constructor(scope: Construct, id: string, api: IGraphqlApi) {
super(scope, id)

const eventBus = new EventBus(this, "filesearch", {})

api.addEventBridgeDataSource("EventBridgeSrc", eventBus)
console.debug("EventBridgeSrc is added")

const policyStatement = new PolicyStatement({
effect: Effect.ALLOW,
actions: ["appsync:GraphQL"],
resources: [`${api.arn}/types/Mutation/*`]
})

const eventBusRole = new Role(this, "AppSyncInvokeRole", {
assumedBy: new ServicePrincipal("events.amazonaws.com"),
inlinePolicies: {
PolicyStatement: new PolicyDocument({
statements: [policyStatement]
})
}
})

new Rule(this, "FileSearch", {
eventBus: eventBus,
ruleName: "broadcastFileSearchUpdates",
eventPattern: {
source: ["amplify.filesearch"],
detailType: ["FileSearchChange"],
detail: {
fileId: [{ exists: true }],
status: ["PENDING", "ATTACHED", "DETACHED"],
message: [{ exists: true }]
}
},
targets: [
new AppSync(api, {
variables: RuleTargetInput.fromObject({
fileId: EventField.fromPath("$.detail.fileId"),
status: EventField.fromPath("$.detail.status"),
message: EventField.fromPath("$.detail.message")
}),
graphQLOperation: `
mutation PublishFileSearchFromEventBridge(
$fileId: String!
$status: String!
$message: String!
) {
publishFileSearchFromEventBridge(fileId: $fileId, status: $status, message: $message) {
fileId
status
message
}
}
`,
eventRole: eventBusRole
})
]
})
}
}
```

I define data backend as this

```
export const data = defineData({
name: "data",
schema,
authorizationModes: {
defaultAuthorizationMode: "userPool"
}
})
```

The stack breaks.
`Error: You must have AWS_IAM authorization mode enabled on your API to configure an AppSync target`

This is the check on construct here, https://github.com/aws/aws-cdk/blob/v2.147.3/packages/aws-cdk-lib/aws-events-targets/lib/appsync.ts#L49

The modes on backend's app sync is empty.

Question: is it still possible to use L2 for the example you have? It seems to support all props. Was this the reason you've use Cnf?