How to assign a private endpoint to a web.app slot using bicep script

I have a application defined as and I am trying to figure out how to map the preview slot to

resource app 'Microsoft.Web/sites@2022-09-01' = {
  name: '${appName}-${env}'
  location: location

  identity: {
    type: 'SystemAssigned'
  }

  properties: {
    serverFarmId: servicePlanId
    httpsOnly: true
    // clientAffinityEnabled: false
    virtualNetworkSubnetId: subnetId

    siteConfig: {
      ftpsState: 'Disabled'
      minTlsVersion: '1.2'
      publicNetworkAccess: 'Disabled'
    }
  }
}

Now I have defined a slot

resource stagingSlot 'Microsoft.Web/sites/slots@2021-02-01' = {
  name: 'preview'
  parent: app
  location: location
  kind: 'app'
  properties: {
    serverFarmId: servicePlanId
  }
}

Now I need to create a private endpoint for the main site and for the slot.

the slot gets created and the endpoint connection also but only to the parent item not the release slot

resource stagingSlotEndpoint 'Microsoft.Web/sites/slots/privateEndpointConnections@2022-03-01' = {
  name: '${appName}-preview'
  kind: 'app'
  parent: stagingSlot
  properties: {
    privateLinkServiceConnectionState: {
      status: 'Approved'
      description: 'Auto-Approved'
      actionsRequired: 'None'
    }
  }
}

To assign a private endpoint connection to a web app slot, you need to use Microsoft.Web/sites/privateEndpointConnections resource type.

Add below code to yours and it will work as expected.

resource prodSiteEndpoint 'Microsoft.Web/sites/privateEndpointConnections@2022-03-01' = {
   name: 'app-produ'
   kind: 'app'
   parent: app
   properties: {
     privateLinkServiceConnectionState: {
     status: 'Approved'
     description: 'Auto-Approved'
     actionsRequired: 'None'
   }
}
 dependsOn: [
   appConfigurationPrivateEndPoint
   appConfigurationPrivateDnsZoneGroup
  ]
}

complete bicep code:

param location string = 'eastus'
param appConfigurationPrivateEp string = 'priend'
param appdns string = 'priend-nic'
resource appServicePlan 'Microsoft.Web/serverfarms@2020-12-01' existing = {
  name: 'uovh4pk4fceb6kic6v5wmtms62'
}
resource app 'Microsoft.Web/sites@2022-09-01' existing = {
  name: 'uovh4pk4fceb6'
}

resource appConfigurationPrivateEndPoint 'Microsoft.Network/privateEndpoints@2021-03-01' existing= {
  name: appConfigurationPrivateEp
}
resource appConfigurationPrivateDnsZoneGroup 'Microsoft.Network/privateEndpoints/privateDnsZoneGroups@2021-03-01' existing= {
  parent: appConfigurationPrivateEp
  name: appdns
}

resource stagingSlot 'Microsoft.Web/sites/slots@2021-02-01' = {
  name: 'stagingpreviewbla'
  parent: app
  location: location
  kind: 'app'
  properties: {
    serverFarmId: appServicePlan.id
  }
}
resource stagingSlotEndpoint 'Microsoft.Web/sites/slots/privateEndpointConnections@2022-03-01' = {
  name: 'app-preview'
  kind: 'app'
  parent: stagingSlot
  properties: {
    privateLinkServiceConnectionState: {
      status: 'Approved'
      description: 'Auto-Approved'
      actionsRequired: 'None'
    }
  }
  dependsOn: [
    appConfigurationPrivateEndPoint
    appConfigurationPrivateDnsZoneGroup
  ]
}
resource prodSiteEndpoint 'Microsoft.Web/sites/privateEndpointConnections@2022-03-01' = {
  name: 'app-produ'
  kind: 'app'
  parent: app
  properties: {
    privateLinkServiceConnectionState: {
      status: 'Approved'
      description: 'Auto-Approved'
      actionsRequired: 'None'
    }
  }
  dependsOn: [
    appConfigurationPrivateEndPoint
    appConfigurationPrivateDnsZoneGroup
  ]
}