Define and run a Great Expectations 1.x Checkpoint with multiple validation definitions and a Slack action

Steps

1. In GX 1.x, create a Data Context with gx.get_context(); then define a Data Source, Data Asset, and Batch Definition using the fluent datasource API rather than the legacy datasource YAML format
2. Build an ExpectationSuite and add individual Expectations to it; create a ValidationDefinition that pairs the Batch Definition with the ExpectationSuite
3. Instantiate a Checkpoint with a list of ValidationDefinition objects, a list of actions, and a result_format (e.g., 'SUMMARY'); save it to the Data Context with context.checkpoints.add(checkpoint)
4. Add a SlackNotificationAction or MicrosoftTeamsNotificationAction to the actions list, providing the webhook URL via an environment variable reference rather than a hardcoded string
5. Run the checkpoint with checkpoint.run(); inspect the CheckpointResult object — it contains a dict of validation results keyed by ValidationDefinition name with pass/fail statistics and the list of failed Expectations