all: add support for ephemeral resources

[SBGoods]

Adds support for ephemeral resource documentation:

• generate: adds documentation generation support for the templates/ephemeral-resources directory and templates/ephemeral-resources.md.tmpl file
• migrate: adds migration support for website/docs/ephemeral-resources and docs/ephemeral-resources subdirectories
• validate: adds ephemeral-resources to the list of valid directory names

[austinvalle]

LGTM, I just had one consideration about the text archive tests.

Ran your changes on the random provider as well and it looks good 👍🏻
hashicorp/terraform-provider-random@main...av/ephemeral-password

[austinvalle]

Not specific to this test, but just a note in general about tests. I see a lot of the internals of resources are already shared with data sources, which I think is fine.

It's a little difficult to see if the expected output below is meant for an ephemeral resource because all of the templates used seem to be geared towards a managed resource (for example, this test has an import.sh), just running through the ephemeral resource code path. For this example, it's not immediately clear how to recreate this test archive, although there isn't an existing ephemeral resource to test it on yet.

We could wait until there is, or for some of the generate ones, just take an upcoming ephemeral resource like random_password as the example (rather then null_ephemeral_resource, which we don't have planned to exist ATM).

[SBGoods]

If we are talking about tests serving as an example of how to use the tool, then I get what you mean. In terms of verifying the functionality, the tests are easy to write because it verifies that the correct files are being created and that all of the template functions are working. But because terraform-plugin-docs doesn't care about whether the schema is "valid" or not and to a certain extent what "types" are, the tests end up being very arbitrary.

We can consider always having at least one real provider test, like the null provider success test, but we don't have a utility provider that implements all schema types now, so we run into the problem of having either an arbitrary provider or using multiple utility providers to cover all types (time and random for example).