Docs: add docs to use aws s3 provider for stackit s3 (#583)

* docs: add docs to use aws s3 provider for stackit s3

* review changes

* fix indent

docs/guides/aws_provider_s3_stackit.md

@@ -0,0 +1,91 @@
+---
+page_title: "Using AWS Provider for STACKIT Object Storage (S3 compatible)"
+---
+# Using AWS Provider for STACKIT Object Storage (S3 compatible)
+
+## Overview
+
+This guide outlines the process of utilizing the [AWS Terraform Provider](https://registry.terraform.io/providers/hashicorp/aws/latest/docs) alongside the STACKIT provider to create and manage STACKIT Object Storage (S3 compatible) ressources.
+
+## Steps
+
+1. **Configure STACKIT Provider**
+
+    First, configure the STACKIT provider to connect to the STACKIT services.
+
+    ```hcl
+    provider "stackit" {
+      region = "eu01"
+    }
+    ```
+
+2. **Define STACKIT Object Storage Bucket**
+
+    Create a STACKIT Object Storage Bucket and obtain credentials for the AWS provider.
+
+    ```hcl
+    resource "stackit_objectstorage_bucket" "example" {
+      project_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+      name       = "example"
+    }
+
+    resource "stackit_objectstorage_credentials_group" "example" {
+      project_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+      name       = "example-credentials-group"
+   }
+
+   resource "stackit_objectstorage_credential" "example" {
+      project_id           = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+      credentials_group_id = stackit_objectstorage_credentials_group.example.credentials_group_id
+      expiration_timestamp = "2027-01-02T03:04:05Z"
+   }
+   ```
+
+3. **Configure AWS Provider**
+
+   Configure the AWS Provider to connect to the STACKIT Object Storage bucket.
+
+    ```hcl
+    provider "aws" {
+      region                      = "eu01"
+      skip_credentials_validation = true
+      skip_region_validation      = true
+      skip_requesting_account_id  = true
+
+      access_key                  = stackit_objectstorage_credential.example.access_key
+      secret_key                  = stackit_objectstorage_credential.example.secret_access_key
+
+      endpoints {
+         s3 = "https://object.storage.eu01.onstackit.cloud"
+      }
+   }
+   ```
+
+4. **Use the provider to manage objects or policies**
+
+    ```hcl
+    resource "aws_s3_object" "test_file" {
+     bucket = stackit_objectstorage_bucket.example.name
+     key    = "hello_world.txt"
+     source = "files/hello_world.txt"
+     content_type = "text/plain"
+     etag = filemd5("files/hello_world.txt")
+    }
+
+    resource "aws_s3_bucket_policy" "allow_public_read_access" {
+     bucket = stackit_objectstorage_bucket.test20.name
+     policy = <<EOF
+     {
+        "Statement":[
+           {
+           "Sid": "Public GET",
+           "Effect":"Allow",
+           "Principal":"*",
+           "Action":"s3:GetObject",
+           "Resource":"urn:sgws:s3:::example/*"
+           }
+        ]
+     }
+     EOF
+    }
+    ```