Add resource for email template settings

[s-nel]

This PR adds a TF resource to manage Okta email template settings (API docs here). The email template settings can be used to control the recipients of different emails.

This is my first time writing a resource, so please review thoroughly 😁

Fixes: #2169

[duytiennguyen-okta]

Hi @s-nel. Thank you for you effort. Can you move from using plugin_sdk to plugin_framework? We are trying to move away from the plugin_sdk as it is outdated. An example can be found here

[s-nel]

Hi @s-nel. Thank you for you effort. Can you move from using plugin_sdk to plugin_framework? We are trying to move away from the plugin_sdk as it is outdated. An example can be found here

Done. I had trouble running the VCR recorded test for plugin framework resources. The plugin SDK ones work fine, but the plugin framework throw dial tcp: lookup oie-00.dne-okta.com: no such host. Is there a different way to run these tests with VCR?

[duytiennguyen-okta]

@s-nel currently the VCR has not been setup to run the plugin framework. As long as your test run, you should be fine

[duytiennguyen-okta]

There is some issue with your code so I bring it in #2179. Close in favor of #2179

[s-nel]

Thanks for your help 🙇