Simplify presigning example (#7065)

* Add advanced presigning example
This changes the "download a file" example to use a custom configuration for the presigned GetObject request.

* Changed from using GetObject as the exemplar for advanced presigning to using PutObject. This lets GetObject be used in doc content as the example for a basic presign operation, while PutObject can be used for more involved presigning ops.

* Make sure the configuration is fully done inside the snippet for example purposes.

---------

Co-authored-by: David Souther <[email protected]>

Author: shepazon

swift/example_code/s3/presigned-urls/Package.swift

@@ -22,17 +22,31 @@ let package = Package(
         .package(
             url: "https://github.com/apple/swift-argument-parser.git",
             branch: "main"
+        ),
+        .package(
+            url: "https://github.com/swift-server/async-http-client.git",
+            from: "1.9.0"
         )
     ],
     targets: [
         // Targets are the basic building blocks of a package, defining a module or a test suite.
-        // Targets can depend on other targets in this package and products from dependencies.
+        // Targets can depend on other targets in this package and products
+        // from dependencies.
         .executableTarget(
-            name: "presigned",
+            name: "presigned-download",
             dependencies: [
                 .product(name: "AWSS3", package: "aws-sdk-swift"),
                 .product(name: "ArgumentParser", package: "swift-argument-parser"),
             ],
-            path: "Sources")
+            path: "Sources/presigned-download"),
+        .executableTarget(
+            name: "presigned-upload",
+            dependencies: [
+                .product(name: "AWSS3", package: "aws-sdk-swift"),
+                .product(name: "ArgumentParser", package: "swift-argument-parser"),
+                .product(name: "AsyncHTTPClient", package: "async-http-client")
+            ],
+            path: "Sources/presigned-upload")
+
     ]
 )