Extract the response interpretation logic out of openapi3 emitter and into http library

common/changes/@cadl-lang/openapi/http-common-responses_2022-03-23-01-35.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@cadl-lang/openapi",
+      "comment": "`@defaultResponse` set status code for model",
+      "type": "minor"
+    }
+  ],
+  "packageName": "@cadl-lang/openapi"
+}

common/changes/@cadl-lang/openapi3/http-common-responses_2022-03-22-21-51.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@cadl-lang/openapi3",
+      "comment": "Moved http response interpretation to @cadl-lang/rest library.",
+      "type": "minor"
+    }
+  ],
+  "packageName": "@cadl-lang/openapi3"
+}

common/changes/@cadl-lang/rest/http-common-responses_2022-03-22-21-51.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@cadl-lang/rest",
+      "comment": "Add logic to interpret the http responses.",
+      "type": "minor"
+    }
+  ],
+  "packageName": "@cadl-lang/rest"
+}

packages/openapi/src/decorators.ts

@@ -5,6 +5,7 @@ import {
   validateDecoratorParamType,
   validateDecoratorTarget,
 } from "@cadl-lang/compiler";
+import { http } from "@cadl-lang/rest";
 import { reportDiagnostic } from "./lib.js";
 
 const operationIdsKey = Symbol();
@@ -64,6 +65,7 @@ export function $defaultResponse({ program }: DecoratorContext, entity: Type) {
   if (!validateDecoratorTarget(program, entity, "@defaultResponse", "Model")) {
     return;
   }
+  http.setStatusCode(program, entity, ["*"]);
   program.stateSet(defaultResponseKey).add(entity);
 }
 

packages/openapi3/src/lib.ts

@@ -27,30 +27,12 @@ export const libDef = {
         default: "Duplicate @body declarations on response type",
       },
     },
-    "duplicate-response": {
-      severity: "error",
-      messages: {
-        default: paramMessage`Multiple return types for content type ${"contentType"} and status code ${"statusCode"}`,
-      },
-    },
     "duplicate-header": {
       severity: "error",
       messages: {
         default: paramMessage`The header ${"header"} is defined across multiple content types`,
       },
     },
-    "content-type-ignored": {
-      severity: "warning",
-      messages: {
-        default: "content-type header ignored because return type has no body",
-      },
-    },
-    "content-type-string": {
-      severity: "error",
-      messages: {
-        default: "contentType parameter must be a string literal or union of string literals",
-      },
-    },
     "status-code-in-default-response": {
       severity: "error",
       messages: {