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/IWireMockOpenApiParser.cs

@@ -0,0 +1,37 @@
+using System.Collections.Generic;
+using System.IO;
+using Microsoft.OpenApi.Models;
+using Microsoft.OpenApi.Readers;
+using WireMock.Admin.Mappings;
+
+namespace WireMock.Net.OpenApiParser
+{
+    /// <summary>
+    /// Parse a OpenApi/Swagger/V2/V3 or Raml to WireMock MappingModels.
+    /// </summary>
+    public interface IWireMockOpenApiParser
+    {
+        /// <summary>
+        /// Generate <see cref="IEnumerable{MappingModel}"/> from an <seealso cref="OpenApiDocument"/>.
+        /// </summary>
+        /// <param name="document">The source OpenApiDocument</param>
+        /// <returns>MappingModel</returns>
+        IEnumerable<MappingModel> FromDocument(OpenApiDocument document);
+
+        /// <summary>
+        /// Generate <see cref="IEnumerable{MappingModel}"/> from a <seealso cref="Stream"/>.
+        /// </summary>
+        /// <param name="stream">The source stream</param>
+        /// <param name="diagnostic">OpenApiDiagnostic output</param>
+        /// <returns>MappingModel</returns>
+        IEnumerable<MappingModel> FromStream(Stream stream, out OpenApiDiagnostic diagnostic);
+
+        /// <summary>
+        /// Generate <see cref="IEnumerable{MappingModel}"/> from a file-path.
+        /// </summary>
+        /// <param name="path">The path to read the OpenApi/Swagger/V2/V3 or Raml file.</param>
+        /// <param name="diagnostic">OpenApiDiagnostic output</param>
+        /// <returns>MappingModel</returns>
+        IEnumerable<MappingModel> FromFile(string path, out OpenApiDiagnostic diagnostic);
+    }
+}