Update Datadog::Dashboards::Dashboard UPDATE handler to check/convert types of sub-models

[opalelement]

What does this PR do?

Fixes #127, allowing updates of Datadog::Dashboards::Dashboard resources created via CFT.

Description of the Change

Sets the validate_and_convert_types _check_type arg to True in update_handler, allowing sub-models of the input value (DashboardDefinition JSON payload) to be deserialized into applicable DataDog API Client models.

Both create_handler and update_handler have comments indicating that this is meant to be True, and it is indeed True in the create_handler, but it appears to have been set to False for the update_handler. As a result, initial creation of dashboard resources succeeds, but dashboards cannot be updated after creation.

When the API client object attempts to serialize the models before sending to the DataDog REST API, it appears to assume all objects will be OpenApiModel subclasses. When _check_type=False, nested JSON objects are not deserialized to their applicable OpenApiModel subclasses, but instead retain their native dict deserialization types. This leads to the following AttributeError:

AttributeError Stack Trace

[ERROR]	2021-04-21T22:24:24.240Z	1819954f-6f4a-4634-b052-641b91b0af44	Exception caught
Traceback (most recent call last):
  File "/var/task/cloudformation_cli_python_lib/resource.py", line 120, in test_entrypoint
    return self._invoke_handler(session, request, action, callback_context)
  File "/var/task/cloudformation_cli_python_lib/resource.py", line 84, in _invoke_handler
    progress = handler(session, request, callback_context)
  File "/var/task/datadog_dashboards_dashboard/handlers.py", line 115, in update_handler
    api_instance.update_dashboard(dashboard_id, dashboard)
  File "/var/task/datadog_api_client/v1/api_client.py", line 757, in __call__
    return self.callable(self, *args, **kwargs)
  File "/var/task/datadog_api_client/v1/api/dashboards_api.py", line 426, in __update_dashboard
    return self.call_with_http_info(**kwargs)
  File "/var/task/datadog_api_client/v1/api_client.py", line 837, in call_with_http_info
    collection_formats=params["collection_format"],
  File "/var/task/datadog_api_client/v1/api_client.py", line 399, in call_api
    _check_type,
  File "/var/task/datadog_api_client/v1/api_client.py", line 167, in __call_api
    body = self.sanitize_for_serialization(body)
  File "/var/task/datadog_api_client/v1/api_client.py", line 257, in sanitize_for_serialization
    return {key: cls.sanitize_for_serialization(val) for key, val in model_to_dict(obj, serialize=True).items()}
  File "/var/task/datadog_api_client/v1/model_utils.py", line 1410, in model_to_dict
    result[attr] = [model_to_dict(x, serialize=serialize) for x in value]
  File "/var/task/datadog_api_client/v1/model_utils.py", line 1410, in <listcomp>
    result[attr] = [model_to_dict(x, serialize=serialize) for x in value]
  File "/var/task/datadog_api_client/v1/model_utils.py", line 1395, in model_to_dict
    if model_instance._composed_schemas:
AttributeError: 'dict' object has no attribute '_composed_schemas'

Verification Process

Change was verified by using aws-sam-cli to invoke the resource provider locally:

sam local invoke TestEntrypoint --event update-event.json

update-event.json

Note that the DatadogCredentials.ApiKey, DatadogCredentials.ApplicationKey, and Id fields (within request.desiredResourceState) must be set appropriately.

{
    "credentials": {
        "accessKeyId": null,
        "secretAccessKey": null,
        "sessionToken": null
    },
    "action": "UPDATE",
    "request": {
        "clientRequestToken": "",
        "desiredResourceState": {
            "Id": "xxx-yyy-zzz",
            "DashboardDefinition": "{\"title\":\"datadog-cloudformation-resources#127\",\"widgets\":[{\"definition\":{\"type\":\"note\",\"content\":\"\"}}],\"layout_type\":\"ordered\"}",
            "DatadogCredentials": {
                "ApiKey": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
                "ApplicationKey": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
            }
        },
        "logicalResourceIdentifier": "TestDashboard"
    }
}

Review checklist (to be filled by reviewers)

• Feature or bug fix MUST have appropriate tests (unit, integration, etc...)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have one changelog/ label attached. If applicable it should have the backward-incompatible label attached.
• PR should not have do-not-merge/ label attached.
• If Applicable, issue must have kind/ and severity/ labels attached at least.

[zippolyte]

LGTM, thanks for the fix