Rename DSA credentials to credential (#76)

* Rename in LogMe

* Rename in other DSA

* Rename examples

* Rename folder names

* Rename in error messages

docs/data-sources/postgresql_credentials.md

@@ -1,42 +0,0 @@
----
-# generated by https://github.com/hashicorp/terraform-plugin-docs
-page_title: "stackit_postgresql_credentials Data Source - stackit"
-subcategory: ""
-description: |-
-  PostgreSQL credentials data source schema.
----
-
-# stackit_postgresql_credentials (Data Source)
-
-PostgreSQL credentials data source schema.
-
-## Example Usage
-
-```terraform
-data "stackit_postgresql_credentials" "example" {
-  project_id     = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
-  instance_id    = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
-  credentials_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
-}
-```
-
-<!-- schema generated by tfplugindocs -->
-## Schema
-
-### Required
-
-- `credentials_id` (String) The credentials ID.
-- `instance_id` (String) ID of the PostgreSQL instance.
-- `project_id` (String) STACKIT project ID to which the instance is associated.
-
-### Read-Only
-
-- `host` (String)
-- `hosts` (List of String)
-- `http_api_uri` (String)
-- `id` (String) Terraform's internal data source. identifier. It is structured as "`project_id`,`instance_id`,`credentials_id`".
-- `name` (String)
-- `password` (String, Sensitive)
-- `port` (Number)
-- `uri` (String)
-- `username` (String)