Add fvalidate to dogshell

[kkyr]

Requirements for Contributing to this repository

• Fill out the template below. Any pull request that does not include enough information to be reviewed in a timely manner may be closed at the maintainers' discretion.
• The pull request must only fix one issue, or add one feature, at the time.
• The pull request must update the test suite to demonstrate the changed functionality.
• After you create the pull request, all status checks must be pass before a maintainer reviews your contribution. For more details, please see CONTRIBUTING.

What does this PR do?

Add fvalidate command to dogshell which validates a monitor using a file as input.

This PR addresses #826

Alternate Designs

No other alternate designs considered.

Possible Drawbacks

N/A

Verification Process

Ran command locally against a monitor defined in a file.

monitor.json

{
	"name": "Sample monitor",
	"type": "query alert",
	"query": "avg(last_5m):avg:system.load.1{host:XYZ} by {host} > 5",
	"message": "Message @team",
	"tags": [],
	"options": {
		"thresholds": {
			"critical": 5,
			"warning": 1
		},
		"notify_audit": true,
		"include_tags": true,
		"new_group_delay": 60
	},
	"priority": 2,
	"restricted_roles": [
		"c3a0b9e2-ec22-11ee-be33-da7ad0900005"
	]
}

➜  Desktop dog --api_host "datadoghq.eu" --pretty monitor fvalidate monitor.json
{}

bad-monitor.json

{
	"name": "Sample monitor",
	"type": "query alert",
	"query": "avg(last_5m):avg:system.load.1{host:XYZ} by {host} > 5",
	"message": "Message @team",
	"tags": [],
	"options": {
		"thresholds": {
			"warning": 1
		},
		"notify_audit": true,
		"include_tags": true,
		"new_group_delay": 60
	},
	"priority": 2,
	"restricted_roles": [
		"c3a0b9e2-ec22-11ee-be33-da7ad0900005"
	]
}

➜  Desktop dog --api_host "datadoghq.eu" --pretty monitor fvalidate bad-monitor.json
{
  "errors": [
    "Alert status is required."
  ]
}

Additional Notes

N/A

Release Notes

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.

[github-actions]

This issue has been automatically marked as stale because it has not had activity in the last 30 days.
Note that the issue will not be automatically closed, but this notification will remind us to investigate why there's been inactivity.