Support smithy models in bundles

Author: rhernandez35

model-bundle/model-bundle-api/src/main/java/software/amazon/smithy/modelbundle/api/ModelBundles.java

@@ -36,8 +36,10 @@ public static Service getService(SmithyBundle smithyBundle) {
     }
 
     private static Model getModel(SmithyBundle bundle) {
+        // TODO: model the type in the returned bundle
+        var suffix = bundle.getModel().startsWith("$version") ? "smithy" : "json";
         var modelAssemble = new ModelAssembler().putProperty(ModelAssembler.ALLOW_UNKNOWN_TRAITS, true)
-                .addUnparsedModel("bundle.json", bundle.getModel())
+                .addUnparsedModel("bundle." + suffix, bundle.getModel())
                 .disableValidation();
         var additionalInput = bundle.getAdditionalInput();
         Model model;

model-bundle/model-bundle-api/src/main/java/software/amazon/smithy/modelbundle/api/PluginProviders.java

@@ -19,7 +19,7 @@ private PluginProviders(Builder builder) {
     public BundlePlugin getPlugin(String identifier, Document input) {
         var provider = providers.get(identifier);
         if (provider == null) {
-            throw new NullPointerException("no auth provider named " + identifier);
+            throw new NullPointerException("No plugin provider named " + identifier);
         }
 
         return provider.createBundlePlugin(input);