Add 5.9 manifest to enforce ExistentialAny

Package@swift-5.9.swift

@@ -0,0 +1,74 @@
+// swift-tools-version:5.9
+import PackageDescription
+
+let package = Package(
+    name: "fluent-kit",
+    platforms: [
+        .macOS(.v10_15),
+        .iOS(.v13),
+        .watchOS(.v6),
+        .tvOS(.v13),
+    ],
+    products: [
+        .library(name: "FluentKit", targets: ["FluentKit"]),
+        .library(name: "FluentBenchmark", targets: ["FluentBenchmark"]),
+        .library(name: "FluentSQL", targets: ["FluentSQL"]),
+        .library(name: "XCTFluent", targets: ["XCTFluent"]),
+    ],
+    dependencies: [
+        .package(url: "https://github.com/apple/swift-nio.git", from: "2.55.0"),
+        .package(url: "https://github.com/apple/swift-log.git", from: "1.5.2"),
+        .package(url: "https://github.com/vapor/sql-kit.git", from: "3.28.0"),
+        .package(url: "https://github.com/vapor/async-kit.git", from: "1.17.0"),
+    ],
+    targets: [
+        .target(
+            name: "FluentKit",
+            dependencies: [
+                .product(name: "NIO", package: "swift-nio"),
+                .product(name: "NIOCore", package: "swift-nio"),
+                .product(name: "Logging", package: "swift-log"),
+                .product(name: "AsyncKit", package: "async-kit"),
+                .product(name: "SQLKit", package: "sql-kit"),
+            ],
+            swiftSettings: swiftSettings
+        ),
+        .target(
+            name: "FluentBenchmark",
+            dependencies: [
+                .target(name: "FluentKit"),
+                .target(name: "FluentSQL"),
+            ],
+            swiftSettings: swiftSettings
+        ),
+        .target(
+            name: "FluentSQL",
+            dependencies: [
+                .target(name: "FluentKit"),
+                .product(name: "SQLKit", package: "sql-kit"),
+            ],
+            swiftSettings: swiftSettings
+        ),
+        .target(
+            name: "XCTFluent",
+            dependencies: [
+                .target(name: "FluentKit"),
+                .product(name: "NIOEmbedded", package: "swift-nio"),
+            ],
+            swiftSettings: swiftSettings
+        ),
+        .testTarget(
+            name: "FluentKitTests",
+            dependencies: [
+                .target(name: "FluentBenchmark"),
+                .target(name: "FluentSQL"),
+                .target(name: "XCTFluent"),
+            ],
+            swiftSettings: swiftSettings
+        ),
+    ]
+)
+
+var swiftSettings: [SwiftSetting] { [
+    .enableUpcomingFeature("ExistentialAny"),
+] }