feat: enable Terraform template-wide variables by default

[mtojek]

Related: coder/terraform-provider-coder#140

Changes:

• drop logic responsible for processing coder provider flags, including feature_use_managed_variables
• feature_use_managed_variables is considered to be the only mode. The flag is ignored in the schema, and will be removed eventually.
• update wording in docs

[johnstcn]

Should be marked as a breaking change:

feat!: enable Terraform template-wide variables by default

Apart from that, what will happen if someone attempts to use an existing template with the below stanza?

provider "coder" {
  feature_use_managed_variables = "true"
}

Will they be directed to remove feature_use_managed_variables?

[mtojek]

Apart from that, what will happen if someone attempts to use an existing template with the below stanza?

Nothing happens, the feature flag is just ignored, hence I was not convinced to mark it as a breaking change. Someday in the future, we will update the coder provider schema to block the flag. Then, the coder will complain about an unknown feature flag.

[johnstcn]

Apart from that, what will happen if someone attempts to use an existing template with the below stanza?

Nothing happens, the feature flag is just ignored, hence I was not convinced to mark it as a breaking change. Someday in the future, we will update the coder provider schema to block the flag. Then, the coder will complain about an unknown feature flag.

Got it - that's fine. 👍

[matifali]

Shouldn't the Coder provider be bumped to 0.10.0? In all of the example templates?

[mtojek]

It is a valid point, but I'd rather do this in a separate PR as more examples will be affected.

[mafredri]

Looks good 👍🏻

[mafredri]

Should this mention the coder provider version as well? (Edit: On second thought, maybe not.)

[mtojek]

In theory, terraform-provider-coder still accepts the feature_use_managed_variables, so maybe not overcomplicate it :)