Update "How to use Terraform to restrict the editing of a dashboard"

[anton-dd]

What does this PR do? What is the motivation?

• We released https://registry.terraform.io/providers/DataDog/datadog/latest/docs/resources/restriction_policy - got a note there that dashboard support is in private beta.
• For dashboards, existing customers that use is_read_only or restricted_roles need to be careful and not use both at the same time, so we offer some additional guidance through Support for now.
• Main goal here is to note document that Terraform Restriction Policies for dashboards are currently in private beta.

Drive-by change - refresh old docs:

1. is_read_only has been deprecated years ago, restricted_roles is marked as deprecated now too: https://docs.datadoghq.com/api/latest/dashboards/#create-a-new-dashboard
2. So, removing the old is_read_only -> restricted_roles migration guidance.

[github-actions[bot]]

Preview links (active after the build_preview check completes)

Modified Files

• https://docs-staging.datadoghq.com/antonkuz/GRACE-1541/tf/dashboards/guide/how-to-use-terraform-to-restrict-dashboard-edit

[drichards-87]

Created DOCS-7430 for Docs Team review.

[sanjaythakkar-dd]

nicely done what are your thoughts on mentioning explicilt that is_read_only is depcreated since its marked as depcreated in tf doc https://registry.terraform.io/providers/DataDog/datadog/latest/docs/resources/dashboard

side note:not part of this PR but maybe we should aos remove the is_read_only in the example for datadog_dashboard

[anton-dd]

@sanjaythakkar-dd

nicely done what are your thoughts on mentioning explicilt that is_read_only is depcreated since its marked as depcreated in tf doc https://registry.terraform.io/providers/DataDog/datadog/latest/docs/resources/dashboard

Thanks! Sounds good, added https://github.com/DataDog/documentation/pull/22186/commits/b3ac6be1cf458327bded376bf09f0cb4df327cb1

side note:not part of this PR but maybe we should aos remove the is_read_only in the example for datadog_dashboard

👍 that was an easy change: https://github.com/DataDog/terraform-provider-datadog/pull/2322

[sanjaythakkar-dd]

Also sorry forgot to mention, do you think we need to say that org as viewer is necessary?

[anton-dd]

Also sorry forgot to mention, do you think we need to say that org as viewer is necessary?

We'll have a more comprehensive doc when we GA RestrictionPolicy TF for dashboards, will note that there. Today customers anyways need to go through support to get this enabled, and we'll inform them there.

[anton-dd]

oops @DrkSephy review re-request click was accidental. Not required.