[APPS-2248] [APPS-2144] App Builder Terraform Provider

[tyffical]

Motivation

• Adds the TF provider for the new App Builder Public API.
• Includes
  • A data source for using Apps outside of resource definitions
  • A resource for managing Apps
  • Support for importing existing Apps as resources.
• Usage: copy and paste App definition JSON from App Builder's JSON editor into Terraform
  • We don't expect users to really create Apps from scratch using TF syntax (too complex). If users come to want this, we will put it in future work.

References

• ADR/Project doc: https://datadoghq.atlassian.net/wiki/spaces/APPS/pages/4285301372/App+Builder+Terraform
• Terraform Provider dev guide: https://datadoghq.atlassian.net/wiki/spaces/API/pages/3881239106/Getting+Started+-+Terraform+Provider
• Synthetics' guide to Terraform Provider dev: https://datadoghq.atlassian.net/wiki/spaces/SYN/pages/2729051036/datadog-api-spec+terraform-provider-datadog
• Ilya's PR for Connections Terraform Provider: [datadog_connection] ACTP-104 Terraform provider for Connections API #2718
• Slack channel for Actions org public API & TF dev: #app-platform-public-apis-and-terraform

Testing

• Local manual testing (CRUD)
• Record test cassettes with test org (TODO, debugging)

Wait Before Merging

• This Public API PR is merged and deployed: https://github.com/DataDog/dd-source/pull/178396
• Other upcoming Public API changes for App Builder are done, expected to be ~ 4 weeks
• Update datadog-api-client-go to latest version to include above changes
• Prepare release as per RELEASING.md: https://github.com/DataDog/terraform-provider-datadog/blob/master/RELEASING.md

Open Questions

• Currently, this resource is called datadog_app. The plan is, in the future, updating this resource with extra structs in order to build an app in TF with TF syntax, strongly typing structs like queries and components.
  • Alternatively, what about creating a separate resource? This would help with making the code cleaner and disambiguate the two use cases. For instance, this resource would instead be datadog_app_json similar to how dashboards has a datadog_dashboard_json, and the non-json usage would be called datadog_app, like how dashboards also has datadog_dashboard.

[tyffical]

• [APPS-2248] [APPS-2144] App Builder Terraform Provider #2723 👈 (View in Graphite)
• master

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