packaging plugin (#254)

motivation: add an easy wasy for lambda users to package their lambda and upload it to AWS

changes:
* add SwiftPM plugin to package the lambda as zipfile, with the verb "archive"
* use docker to build and package the lambda(s) on macOS and non-amazonlinux
* build directly on when on amazonlinux, zip correctly

Co-authored-by: Yim Lee <yim_lee@apple.com>
Co-authored-by: Fabian Fett <fabianfett@apple.com>

Author: 3 people

Package@swift-5.6.swift

@@ -0,0 +1,66 @@
+// swift-tools-version:5.6
+
+import PackageDescription
+
+let package = Package(
+    name: "swift-aws-lambda-runtime",
+    products: [
+        // this library exports `AWSLambdaRuntimeCore` and adds Foundation convenience methods
+        .library(name: "AWSLambdaRuntime", targets: ["AWSLambdaRuntime"]),
+        // this has all the main functionality for lambda and it does not link Foundation
+        .library(name: "AWSLambdaRuntimeCore", targets: ["AWSLambdaRuntimeCore"]),
+        // plugin to package the lambda, creating an archive that can be uploaded to AWS
+        .plugin(name: "AWSLambdaPackager", targets: ["AWSLambdaPackager"]),
+        // for testing only
+        .library(name: "AWSLambdaTesting", targets: ["AWSLambdaTesting"]),
+    ],
+    dependencies: [
+        .package(url: "https://github.com/apple/swift-nio.git", .upToNextMajor(from: "2.33.0")),
+        .package(url: "https://github.com/apple/swift-log.git", .upToNextMajor(from: "1.4.2")),
+        .package(url: "https://github.com/swift-server/swift-backtrace.git", .upToNextMajor(from: "1.2.3")),
+    ],
+    targets: [
+        .target(name: "AWSLambdaRuntime", dependencies: [
+            .byName(name: "AWSLambdaRuntimeCore"),
+            .product(name: "NIOCore", package: "swift-nio"),
+            .product(name: "NIOFoundationCompat", package: "swift-nio"),
+        ]),
+        .target(name: "AWSLambdaRuntimeCore", dependencies: [
+            .product(name: "Logging", package: "swift-log"),
+            .product(name: "Backtrace", package: "swift-backtrace"),
+            .product(name: "NIOHTTP1", package: "swift-nio"),
+            .product(name: "NIOCore", package: "swift-nio"),
+            .product(name: "NIOConcurrencyHelpers", package: "swift-nio"),
+            .product(name: "NIOPosix", package: "swift-nio"),
+        ]),
+        .plugin(
+            name: "AWSLambdaPackager",
+            capability: .command(
+                intent: .custom(
+                    verb: "archive",
+                    description: "Archive the Lambda binary and prepare it for uploading to AWS. Requires docker on macOS or non Amazonlinux 2 distributions."
+                )
+            )
+        ),
+        .testTarget(name: "AWSLambdaRuntimeCoreTests", dependencies: [
+            .byName(name: "AWSLambdaRuntimeCore"),
+            .product(name: "NIOTestUtils", package: "swift-nio"),
+            .product(name: "NIOFoundationCompat", package: "swift-nio"),
+        ]),
+        .testTarget(name: "AWSLambdaRuntimeTests", dependencies: [
+            .byName(name: "AWSLambdaRuntimeCore"),
+            .byName(name: "AWSLambdaRuntime"),
+        ]),
+        // testing helper
+        .target(name: "AWSLambdaTesting", dependencies: [
+            .byName(name: "AWSLambdaRuntime"),
+            .product(name: "NIO", package: "swift-nio"),
+        ]),
+        .testTarget(name: "AWSLambdaTestingTests", dependencies: ["AWSLambdaTesting"]),
+        // for perf testing
+        .executableTarget(name: "MockServer", dependencies: [
+            .product(name: "NIOHTTP1", package: "swift-nio"),
+            .product(name: "NIO", package: "swift-nio"),
+        ]),
+    ]
+)