message: Fix base class for SearchIndexerDataNoneIdentity and SearchIndexerDatauserAssignedIdentity
diff: "required": [
  "@odata.type"
  ],
  - "description": "Base type for data identities."
  + "description": "Abstract base type for data identities."
  },
  "SearchIndexerDataNoneIdentity": {
  "description": "Clears the identity property of a datasource.",
  "x-ms-discriminator-value": "#Microsoft.Azure.Search.SearchIndexerDataNoneIdentity",
  "allOf": [
  {
  - "$ref": "#/definitions/DataChangeDetectionPolicy"
  + "$ref": "#/definitions/SearchIndexerDataIdentity"
  }
  ]
  },
  "x-ms-discriminator-value": "#Microsoft.Azure.Search.SearchIndexerDataUserAssignedIdentity",
  "allOf": [
  {
  - "$ref": "#/definitions/DataChangeDetectionPolicy"
  + "$ref": "#/definitions/SearchIndexerDataIdentity"
  }
  ],
  "properties": {
  