Add RequestCompression trait

Sources/SotoSmithy/Core/Smithy.swift

@@ -106,6 +106,7 @@ public struct Smithy {
                 PaginatedTrait.self,
                 HttpChecksumRequiredTrait.self,
                 HttpChecksumTrait.self,
+                RequestCompression.self,
                 // resource traits
                 NoReplaceTrait.self,
                 ReferencesTrait.self,

Sources/SotoSmithy/Traits/Types/BehaviourTraits.swift

@@ -91,3 +91,13 @@ public struct UnitTypeTrait: StaticTrait {
     public var selector: Selector { TypeSelector<UnitShape>() }
     public init() {}
 }
+
+/// Defines the shape to be a unit type similar to Void or None
+public struct RequestCompression: StaticTrait {
+    public static var staticName: ShapeId = "smithy.api#requestCompression"
+    public var selector: Selector { TypeSelector<OperationShape>() }
+    public let encodings: [String]
+    public init(encodings: [String]) {
+        self.encodings = encodings
+    }
+}

Tests/SotoSmithyTests/TraitTests.swift

@@ -465,4 +465,29 @@ class TraitTests: XCTestCase {
         let model = try Smithy().parse(smithy)
         try model.validate()
     }
+
+    func testRequestCompression() throws {
+        let smithy = """
+        $version: "2"
+        namespace smithy.example
+
+        @requestCompression(
+            encodings: ["gzip"]
+        )
+        operation PutWithContentEncoding {
+            input: PutWithContentEncodingInput
+        }
+
+        @input
+        structure PutWithContentEncodingInput {
+            @httpHeader("Content-Encoding")
+            customEncoding: String // brotli
+
+            @httpPayload
+            data: String
+        }
+        """
+        let model = try Smithy().parse(smithy)
+        try model.validate()
+    }
 }