Merge pull request #110 from hashicorp/saml-lib-readme

Add SAML to README

README.md

@@ -216,6 +216,51 @@ if result.Success {
   // user successfully authenticated...
   if len(result.Groups) > 0 {
     // we found some groups associated with the authenticated user...
-  } 
+  }
 }
 ```
+
+### [`saml package`](./saml)
+
+A package for writing clients that integrate with SAML Providers.
+
+The SAML library orients mainly on the implementation profile for
+[federation interoperability](https://kantarainitiative.github.io/SAMLprofiles/fedinterop.html)
+(also known as interoperable SAML), a set of software conformance requirements
+intended to facilitate interoperability within the context of full mesh identity
+federations. It supports the Web Browser SSO profile with HTTP-Post and
+HTTP-Redirect as supported service bindings. The default SAML settings follow
+the requirements of the interoperable SAML
+[deployment profile](https://kantarainitiative.github.io/SAMLprofiles/saml2int.html#_service_provider_requirements).
+
+#### Example usage
+
+```go
+    // Create a new saml config providing the necessary provider information:
+    cfg, err := saml.NewConfig(<entityID>, <acs>, <metadata>, options...)
+	// handle error
+
+    // Use the config to create the service provider:
+    sp, err := saml.NewServiceProvider(cfg)
+    // handle error
+
+    // With the service provider you can create saml authentication requests:
+
+    // Generate a saml auth request with HTTP Post-Binding
+    template, err := sp.AuthRequestPost("relay state", options...)
+    // handle error
+
+    // Generate a saml auth request with HTTP Request-Binding
+    redirectURL, err := sp.AuthRequestRedirect("relay state", options...)
+    // handle error
+
+    // Parsing a SAML response:
+    r.ParseForm()
+    samlResp := r.PostForm.Get("SAMLResponse")
+
+    response, err := sp.ParseResponse(samlResp, "Response ID", options...)
+    // handle error
+```
+
+You can find the full demo code in the [`saml/demo`](./saml/demo/main.go)
+package.