Add experimentalIdentityAndAuth flag

Add the experimental feature flag for identity and auth `experimentalIdentityAndAuth` in `TypeScriptSettings`.

- For `AddHttpApiKeyAuthPlugin`, make the current behavior the control branch for `experimentalIdentityAndAuth`.
- Add a test projection in `smithy-typescript-codegen-test` for `experimentalIdentityAndAuth`.

Also, add a section in `CONTRIBUTING.md` about experimental features in `smithy-typescript`.

Author: Steven Yuan

CONTRIBUTING.md

@@ -20,6 +20,18 @@ In order to utilise this feature, create a file `local.properties` in the projec
 smithy=/Volumes/workplace/smithy
 ```
 
+## Experimental Features
+
+The `smithy-typescript` repository is under heavy development, and has experimental features that can affect consumers
+of code generation packages and TypeScript packages. These features are enabled via opt-in settings in
+`smithy-build.json`. Note that any contributions related to these features MUST be reviewed carefully for opt-in
+behavior via feature flags as to not break any existing customers. Here are the experimental features that are currently
+under development:
+
+Experimental Feature | Flag                          | Description
+---------------------|-------------------------------|------------
+Identity & Auth      | `experimentalIdentityAndAuth` | Standardize identity and auth integrations to match the Smithy specification (see [Authentication Traits](https://smithy.io/2.0/spec/authentication-traits.html)). Newer capabilities include support for multiple auth schemes, `@optionalAuth`, and standardized identity interfaces for authentication schemes both in code generation and TypeScript packages. In `smithy-typescript`, `@httpApiKeyAuth` will be updated to use the new standardized interfaces. In `aws-sdk-js-v3` (`smithy-typescript`'s largest customer), this will affect `@aws.auth#sigv4` and `@httpBearerAuth` implementations, but is planned to be completely backwards-compatible.
+
 ## Reporting Bugs/Feature Requests
 
 We welcome you to use the GitHub issue tracker to report bugs or suggest features.

smithy-typescript-codegen-test/smithy-build.json

@@ -23,6 +23,21 @@
                     "disableDefaultValidation": true
                 }
             }
+        },
+        "client-experimental-identity-and-auth": {
+            "plugins": {
+                "typescript-codegen": {
+                    "service": "example.weather#Weather",
+                    "targetNamespace": "Weather",
+                    "package": "weather",
+                    "packageVersion": "0.0.1",
+                    "packageJson": {
+                        "license": "Apache-2.0",
+                        "private": true
+                    },
+                    "experimentalIdentityAndAuth": true
+                }
+            }
         }
     },
     "plugins": {

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/TypeScriptSettings.java

@@ -58,6 +58,7 @@ public final class TypeScriptSettings {
     private static final String PRIVATE = "private";
     private static final String PACKAGE_MANAGER = "packageManager";
     private static final String CREATE_DEFAULT_README = "createDefaultReadme";
+    private static final String EXPERIMENTAL_IDENTITY_AND_AUTH = "experimentalIdentityAndAuth";
 
     private String packageName;
     private String packageDescription = "";
@@ -74,6 +75,7 @@ public final class TypeScriptSettings {
         RequiredMemberMode.NULLABLE;
     private PackageManager packageManager = PackageManager.YARN;
     private boolean createDefaultReadme = false;
+    private boolean experimentalIdentityAndAuth = false;
 
     @Deprecated
     public static TypeScriptSettings from(Model model, ObjectNode config) {
@@ -107,6 +109,8 @@ public static TypeScriptSettings from(Model model, ObjectNode config, ArtifactTy
         settings.setPrivate(config.getBooleanMember(PRIVATE).map(BooleanNode::getValue).orElse(false));
         settings.setCreateDefaultReadme(
                 config.getBooleanMember(CREATE_DEFAULT_README).map(BooleanNode::getValue).orElse(false));
+        settings.setExperimentalIdentityAndAuth(
+                config.getBooleanMemberOrDefault(EXPERIMENTAL_IDENTITY_AND_AUTH, false));
         settings.setPackageManager(
                 config.getStringMember(PACKAGE_MANAGER)
                     .map(s -> PackageManager.fromString(s.getValue()))
@@ -352,6 +356,31 @@ public void setPackageManager(PackageManager packageManager) {
         this.packageManager = packageManager;
     }
 
+    /**
+     * Returns whether to use experimental identity and auth.
+     *
+     * @return if experimental identity and auth should used. Default: false
+     */
+    public boolean getExperimentalIdentityAndAuth() {
+        return experimentalIdentityAndAuth;
+    }
+
+    /**
+     * Sets whether experimental identity and auth should be used.
+     *
+     * @param experimentalIdentityAndAuth whether experimental identity and auth should be used.
+     */
+    public void setExperimentalIdentityAndAuth(boolean experimentalIdentityAndAuth) {
+        if (experimentalIdentityAndAuth) {
+            LOGGER.warning("""
+                Experimental identity and auth is in development, and is subject to \
+                breaking changes. Behavior may NOT have the same feature parity as \
+                non-experimental behavior. This setting is also subject to removal \
+                when the feature is completed.""");
+        }
+        this.experimentalIdentityAndAuth = experimentalIdentityAndAuth;
+    }
+
     /**
      * Gets the corresponding {@link ServiceShape} from a model.
      *

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/AddHttpApiKeyAuthPlugin.java

@@ -76,6 +76,7 @@ public List<RuntimeClientPlugin> getClientPlugins() {
                             .name("resolveHttpApiKeyAuthConfig")
                             .build())
                     .servicePredicate((m, s) -> hasEffectiveHttpApiKeyAuthTrait(m, s))
+                    .settingsPredicate((m, s, settings) -> !settings.getExperimentalIdentityAndAuth())
                     .build(),
 
             // Add the middleware to operations that use HTTP API key authorization.
@@ -96,21 +97,25 @@ public List<RuntimeClientPlugin> getClientPlugins() {
                             .keySet()
                             .contains(HttpApiKeyAuthTrait.ID)
                             && !o.hasTrait(OptionalAuthTrait.class))
+                    .settingsPredicate((m, s, settings) -> !settings.getExperimentalIdentityAndAuth())
                     .build()
         );
     }
 
     @Override
     public void customize(TypeScriptCodegenContext codegenContext) {
-        TypeScriptSettings settings = codegenContext.settings();
-        Model model = codegenContext.model();
-        BiConsumer<String, Consumer<TypeScriptWriter>> writerFactory = codegenContext.writerDelegator()::useFileWriter;
+        if (!codegenContext.settings().getExperimentalIdentityAndAuth()) {
+            TypeScriptSettings settings = codegenContext.settings();
+            Model model = codegenContext.model();
+            BiConsumer<String, Consumer<TypeScriptWriter>> writerFactory =
+                codegenContext.writerDelegator()::useFileWriter;
 
-        writeAdditionalFiles(settings, model, writerFactory);
+            writeAdditionalFiles(settings, model, writerFactory);
 
-        writerFactory.accept(Paths.get(CodegenUtils.SOURCE_FOLDER, "index.ts").toString(), writer -> {
-            writeAdditionalExports(settings, model, writer);
-        });
+            writerFactory.accept(Paths.get(CodegenUtils.SOURCE_FOLDER, "index.ts").toString(), writer -> {
+                writeAdditionalExports(settings, model, writer);
+            });
+        }
     }
 
     private void writeAdditionalFiles(