Lack of idempotency

[itaispiegel]

Describe the bug
The provider isn't idempotent. When trying to use the provider to apply a configuration of resources which already exist, an error is raised saying that the resource already exists.

Steps to reproduce

1. Create a tenant manually on the website. Say its name is "tenant".
2. Define the following resource:

resource "octopusdeploy_tenant" "tenant" {
  name        = "tenant"
}

3. Apply the configuration, and expect to receive the following output:

|
│ Error: octopus deploy api returned an error on endpoint /api/Spaces-1/tenants - [A tenant with this name already exists. Please choose a different name.]
│ 
│   with octopusdeploy_tenant.tenant,
│   on main.tf line 17, in resource "octopusdeploy_tenant" "tenant":
│   17: resource "octopusdeploy_tenant" "tenant" {
│ 
╵

Expected behavior
The expected behavior is that Terraform should return without making any changes.

Environment and versions:

• OS: OSX
• Octopus Server Version: 2023.4.4798
• Terraform Version: v1.5.2
• Octopus Terraform Provider Version: v0.12.7