Created Cors (markdown)

Cors.md

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+# Issue
+When calling WireMock.Net Server from a frontend applicatie (React / Angular), a CORS error is returned:
+
+```
+Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:9091/__admin/mappings.
+(Reason: CORS header ‘Access-Control-Allow-Origin’ missing). Status code: 200.
+```
+
+# Solution
+Cors support is not enabled by default, you can enable it yourself when configuring WireMock.Net Server, like:
+
+``` c#
+var settings = new WireMockServerSettings
+{
+   // Other settings
+};
+
+/* Enable Cors */
+var policyName = "MyPolicy";
+settings.AdditionalServiceRegistration = services =>
+{
+    services.AddCors(corsOptions =>
+        corsOptions.AddPolicy(policyName, // ◀️ MyPolicy
+            corsPolicyBuilder =>
+            {
+                corsPolicyBuilder
+                    .AllowAnyHeader()
+                    .AllowAnyMethod()
+                    .AllowAnyOrigin();
+            }));
+
+    settings.Logger.Debug("Enable Cors");
+};
+
+/* Use Cors */
+settings.PreWireMockMiddlewareInit = app =>
+{
+    var appBuilder = (IApplicationBuilder)app;
+    appBuilder.UseCors(policyName); // ◀️ MyPolicy
+
+    settings.Logger.Debug("Use Cors");
+};
+
+// Start Server
+var server = WireMockServer.Start(settings);
+```
+
+See also [WireMock.Net.StandAlone.NETCoreApp/Program.cs](https://github.com/WireMock-Net/WireMock.Net/blob/master/examples/WireMock.Net.StandAlone.NETCoreApp/Program.cs#L39).
+
+
+# :books: References
+- https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS/Errors/CORSMissingAllowOrigin
+- https://stackoverflow.com/questions/31942037/how-to-enable-cors-in-asp-net-core