When creating volumes, "region" is not being converted to lowercase letters and causes an error during terraform apply

[nixc0]

Bug Report

---

Describe the bug

When using uppercase letters in region (example NYC3 or AMS1) when creating a new volume causes terraform apply to fail

Affected Resource(s)

• digitalocean_volume

If this issue appears to affect multiple resources, it may be an issue with
Terraform's core, so please mention this. -->

Expected Behavior

Region should have been converted to lowercase nyc3 and volume created. This is the behavior that happens when I create a Droplet using the region NYC3.

Actual Behavior

When running terraform apply the following error is produced.
Error: Error creating Volume: POST https://api.digitalocean.com/v2/volumes: 403 (request "51693f34-b786-44e3-8fe1-8ac3dcbe7e1a") failed to create volume: volume allocation operations not allowed in this region at this time

Steps to Reproduce

Terraform Configuration Files
Here is an example of the Droplet I am creating at the same time using "NYC3" as the region instead of "nyc3". This works as expected.

terraform {
  required_providers {
    digitalocean = {
      source = "digitalocean/digitalocean"
      version = "~> 2.0"
    }
  }
}
variable "do_token" {}

provider "digitalocean" {
  token = var.do_token
}
resource "digitalocean_droplet" "www-1" {
    image = "ubuntu-20-04-x64"
    name = "www-1"
    region = "NYC3"
    size = "s-1vcpu-1gb"
}

During the same plan and apply, below is the configuration file for the volume I am creating with "NYC3" as the region instead of "nyc3".

resource "digitalocean_volume" "foobar" {
  region                  = "NYC3"
  name                    = "baz"
  size                    = 100
  initial_filesystem_type = "ext4"
  description             = "an example volume"
}

Terraform version

I replicated this issue on 1.3.4 & 1.3.5

Debug Output

https://gist.github.com/nixc0/0864906078831e9a65bf6ce7c8f16f31
Panic Output

Additional context

If I'm not mistaken, this line

terraform-provider-digitalocean/digitalocean/resource_digitalocean_volume.go

Line 32 in 2a413c8

return strings.ToLower(val.(string))

should be converting this "NYC3" to "nyc3" in order to work with the all lowercase requirements of the DO API.

[andrewsomething]

Fixed via #1074