Example storage class for stackit database does not work

[dome-meg]

Wrong class in example Code

similiar to #1464

You provide an example in the docs for an storage class.

• https://registry.terraform.io/providers/stackitcloud/stackit/latest/docs/resources/postgresflex_instance

resource "stackit_postgresflex_instance" "example" {
  # ...
  storage = {
    class = "class" # <---
    size  = 5
  }
}

but this storage class does not exist.

Replace it with a working example: premium-perf2-stackit.

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DX is a pain Part 2

I had to look up the available classes of storage in the portal https://portal.stackit.cloud/postgres-flex/instances/wizard
At least this time (not like in #1464 ) the names are directly visible and I dont need to look into the HTML.
Would be super cool to provide a link in the docs to all storage classes and provide a WORKING example.

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I really appreciate that stackit want to be a EU baked hyperscaler, but you guys have to eat your own dogfood to improve the developer experiance, else you will loose potentiall customers because dev's are complaining that your documentation is bad / not working.