storageSizeGB is required for Postgres Flexible Server

[tssdavey]

I believe that this should be required https://github.com/Azure/azure-rest-api-specs/blob/d736c01be58a43b9297ed4f602c5018cd4fb8a5d/specification/postgresql/resource-manager/Microsoft.DBforPostgreSQL/preview/2023-03-01-preview/FlexibleServers.json#L726C10-L726C23

I'm using bicep as documented here (https://learn.microsoft.com/en-us/azure/templates/microsoft.dbforpostgresql/flexibleservers?pivots=deployment-language-bicep), but I believe this issue is with the rest api being called under the hood, as bicep doesn't see this attribute as required, because the rest api doesn't.

Steps to recreate -

resource postgresdatabase 'Microsoft.DBforPostgreSQL/flexibleServers@2023-03-01-preview' = {
  name: 'testpostgresdatabase'
  location: uksouth
  sku: {
    name: 'Standard_B1ms'
    tier: 'Burstable'
  }
  properties: {
    createMode: 'Default'
    administratorLogin: 'mypguser'
    administratorLoginPassword: 'MyS3curePa55w0rD!'
    authConfig: {
      passwordAuth: 'Enabled'
      activeDirectoryAuth: 'Disabled'
    }
    version: '15'
  }
}

Results in '500 Internal Server Error'

resource postgresdatabase 'Microsoft.DBforPostgreSQL/flexibleServers@2023-03-01-preview' = {
  name: 'testpostgresdatabase'
  location: uksouth
  sku: {
    name: 'Standard_B1ms'
    tier: 'Burstable'
  }
  properties: {
    createMode: 'Default'
    administratorLogin: 'mypguser'
    administratorLoginPassword: 'MyS3curePa55w0rD!'
    authConfig: {
      passwordAuth: 'Enabled'
      activeDirectoryAuth: 'Disabled'
    }
    storage: {
      storageSizeGB: 32
    }
    version: '15'
  }
}

Creates successfully.