feat: add post3 s3 proxy for postgresql

Signed-off-by: kjuulh <contact@kjuulh.io>

crates/post3-sdk/examples/metadata.rs

@@ -0,0 +1,78 @@
+//! Demonstrate custom metadata (x-amz-meta-*) with post3.
+//!
+//! Prerequisites: post3-server running on localhost:9000
+//!   mise run up && mise run dev
+//!
+//! Run:
+//!   cargo run -p post3-sdk --example metadata
+
+use post3_sdk::Post3Client;
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    let endpoint = std::env::var("POST3_ENDPOINT")
+        .unwrap_or_else(|_| "http://localhost:9000".to_string());
+    let client = Post3Client::new(&endpoint);
+
+    client.create_bucket("meta-bucket").await?;
+
+    // Use the inner aws-sdk-s3 client to set custom metadata
+    let inner = client.inner();
+    println!("Putting object with custom metadata...");
+    inner
+        .put_object()
+        .bucket("meta-bucket")
+        .key("report.pdf")
+        .body(Vec::from(&b"fake pdf content"[..]).into())
+        .content_type("application/pdf")
+        .metadata("author", "alice")
+        .metadata("department", "engineering")
+        .metadata("version", "2")
+        .send()
+        .await?;
+
+    // Retrieve metadata via head_object
+    let head = inner
+        .head_object()
+        .bucket("meta-bucket")
+        .key("report.pdf")
+        .send()
+        .await?;
+
+    println!("Content-Type: {:?}", head.content_type());
+    println!("Content-Length: {:?}", head.content_length());
+    println!("ETag: {:?}", head.e_tag());
+    if let Some(metadata) = head.metadata() {
+        println!("Custom metadata:");
+        for (k, v) in metadata {
+            println!("  x-amz-meta-{}: {}", k, v);
+        }
+    }
+
+    // Retrieve the full object with metadata
+    let resp = inner
+        .get_object()
+        .bucket("meta-bucket")
+        .key("report.pdf")
+        .send()
+        .await?;
+
+    println!("\nGet object response:");
+    println!("  Content-Type: {:?}", resp.content_type());
+    if let Some(metadata) = resp.metadata() {
+        println!("  Metadata:");
+        for (k, v) in metadata {
+            println!("    x-amz-meta-{}: {}", k, v);
+        }
+    }
+
+    let body = resp.body.collect().await?.into_bytes();
+    println!("  Body: {}", String::from_utf8_lossy(&body));
+
+    // Cleanup
+    client.delete_object("meta-bucket", "report.pdf").await?;
+    client.delete_bucket("meta-bucket").await?;
+    println!("\nDone!");
+
+    Ok(())
+}