docs (saml): add a pkg level readme and a godoc link (#111)

README.md

@@ -222,6 +222,8 @@ if result.Success {
 
 ### [`saml package`](./saml)
 
+[![Go Reference](https://pkg.go.dev/badge/github.com/hashicorp/cap/saml.svg)](https://pkg.go.dev/github.com/hashicorp/cap/saml)
+
 A package for writing clients that integrate with SAML Providers.
 
 The SAML library orients mainly on the implementation profile for

saml/README.md

@@ -0,0 +1,47 @@
+
+# [`saml package`](./saml)
+
+[![Go Reference](https://pkg.go.dev/badge/github.com/hashicorp/cap/saml.svg)](https://pkg.go.dev/github.com/hashicorp/cap/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.