An OpenApi (swagger) parser to generate MappingModel or mapping.json file (#479)

* wip

* .

* .

* nuget

* .

* .

* WithMappingModel

* tests

* json

* codefactor

* sign

* .

* interface

* sln

* comments

src/WireMock.Net.OpenApiParser/Extensions/OpenApiSchemaExtensions.cs

@@ -0,0 +1,92 @@
+using Microsoft.OpenApi.Any;
+using Microsoft.OpenApi.Interfaces;
+using Microsoft.OpenApi.Models;
+using WireMock.Net.OpenApiParser.Types;
+
+namespace WireMock.Net.OpenApiParser.Extensions
+{
+    internal static class OpenApiSchemaExtensions
+    {
+        /// <summary>
+        /// https://stackoverflow.com/questions/48111459/how-to-define-a-property-that-can-be-string-or-null-in-openapi-swagger
+        /// </summary>
+        public static bool TryGetXNullable(this OpenApiSchema schema, out bool value)
+        {
+            value = false;
+
+            if (schema.Extensions.TryGetValue("x-nullable", out IOpenApiExtension e) && e is OpenApiBoolean openApiBoolean)
+            {
+                value = openApiBoolean.Value;
+                return true;
+            }
+
+            return false;
+        }
+
+        public static SchemaType GetSchemaType(this OpenApiSchema schema)
+        {
+            switch (schema?.Type)
+            {
+                case "object":
+                    return SchemaType.Object;
+
+                case "array":
+                    return SchemaType.Array;
+
+                case "integer":
+                    return SchemaType.Integer;
+
+                case "number":
+                    return SchemaType.Number;
+
+                case "boolean":
+                    return SchemaType.Boolean;
+
+                case "string":
+                    return SchemaType.String;
+
+                case "file":
+                    return SchemaType.File;
+
+                default:
+                    return SchemaType.Unknown;
+            }
+        }
+
+        public static SchemaFormat GetSchemaFormat(this OpenApiSchema schema)
+        {
+            switch (schema?.Format)
+            {
+                case "float":
+                    return SchemaFormat.Float;
+
+                case "double":
+                    return SchemaFormat.Double;
+
+                case "int32":
+                    return SchemaFormat.Int32;
+
+                case "int64":
+                    return SchemaFormat.Int64;
+
+                case "date":
+                    return SchemaFormat.Date;
+
+                case "date-time":
+                    return SchemaFormat.DateTime;
+
+                case "password":
+                    return SchemaFormat.Password;
+
+                case "byte":
+                    return SchemaFormat.Byte;
+
+                case "binary":
+                    return SchemaFormat.Binary;
+
+                default:
+                    return SchemaFormat.Undefined;
+            }
+        }
+    }
+}