Update Error for Sanitizer Add (#7005)

* create cherry-pickable commit
* update tests to reflect new logged outputs

tools/test-proxy/Azure.Sdk.Tools.TestProxy.Tests/AdminTests.cs

@@ -882,7 +882,7 @@ public async Task TestAddSanitizerThrowsOnMissingRequiredArgument()
             );
 
             Assert.True(assertion.StatusCode.Equals(HttpStatusCode.BadRequest));
-            Assert.Contains("Required parameter key System.String target was not found in the request body.", assertion.Message);
+            Assert.Contains("Required parameter key \"target\" was not found in the request body.", assertion.Message);
         }
 
         [Fact]

tools/test-proxy/Azure.Sdk.Tools.TestProxy/Admin.cs

@@ -215,7 +215,7 @@ private object GenerateInstance(string typePrefix, string name, HashSet<string>
                     {
                         if (!acceptableEmptyArgs.Contains(param.Name))
                         {
-                            throw new HttpException(HttpStatusCode.BadRequest, $"Parameter {param.Name} was passed with no value. Please check the request body and try again.");
+                            throw new HttpException(HttpStatusCode.BadRequest, $"Parameter \"{param.Name}\" was passed with no value. Please check the request body and try again.");
                         }
                     }
 
@@ -229,7 +229,7 @@ private object GenerateInstance(string typePrefix, string name, HashSet<string>
                     }
                     else
                     {
-                        throw new HttpException(HttpStatusCode.BadRequest, $"Required parameter key {param} was not found in the request body.");
+                        throw new HttpException(HttpStatusCode.BadRequest, $"Required parameter key \"{param.Name}\" was not found in the request body.");
                     }
                 }
             }