Add nullable operator for nullable types

Author: MaggieKimani1

src/Microsoft.OpenApi/Extensions/OpenApiTypeMapper.cs

@@ -115,10 +115,10 @@ public static Type MapOpenApiPrimitiveTypeToSimpleType(this OpenApiSchema schema
                 ("string", "uri", false) => typeof(Uri),
                 ("integer", "int32", true) => typeof(int?),
                 ("integer", "int64", true) => typeof(long?),
-                ("integer", null, true) => typeof(int),
+                ("integer", null, true) => typeof(int?),
                 ("number", "float", true) => typeof(float?),
                 ("number", "double", true) => typeof(double?),
-                ("number", null, true) => typeof(double),
+                ("number", null, true) => typeof(double?),
                 ("number", "decimal", true) => typeof(decimal?),
                 ("string", "byte", true) => typeof(byte?),
                 ("string", "date-time", true) => typeof(DateTimeOffset?),

test/Microsoft.OpenApi.Tests/Extensions/OpenApiTypeMapperTests.cs

@@ -25,7 +25,7 @@ public class OpenApiTypeMapperTests
         {
             new object[] { new OpenApiSchema { Type = "integer", Format = "int32"}, typeof(int) },
             new object[] { new OpenApiSchema { Type = "integer", Format = null, Nullable = false}, typeof(int) },
-            new object[] { new OpenApiSchema { Type = "integer", Format = null, Nullable = true}, typeof(int) },
+            new object[] { new OpenApiSchema { Type = "integer", Format = null, Nullable = true}, typeof(int?) },
             new object[] { new OpenApiSchema { Type = "string" }, typeof(string) },
             new object[] { new OpenApiSchema { Type = "number", Format = "double" }, typeof(double) },
             new object[] { new OpenApiSchema { Type = "number", Format = "float", Nullable = true }, typeof(float?) },