Update docs

README.md

@@ -6,6 +6,7 @@ INWX for [`libdns`](https://github.com/libdns/libdns)
 
 This package implements the [libdns interfaces](https://github.com/libdns/libdns) for [INWX](https://www.inwx.de/en), allowing you to manage DNS records.
 
+This provider uses the JSON-RPC API, which is described in the [official documentation](https://www.inwx.de/en/help/apidoc).
 
 Authenticating
 ==============
@@ -14,7 +15,7 @@ To authenticate you need to supply following credentials:
 
   * Your INWX username
   * Your INWX password
-  * A shared secret if you have enabled two-factor authentication
+  * A shared secret if you have enabled Mobile TAN (two-factor authentication)
 
 
 Example

provider.go

@@ -13,10 +13,17 @@ import (
 
 // Provider facilitates DNS record manipulation with INWX.
 type Provider struct {
-	Username     string `json:"username,omitempty"`
-	Password     string `json:"password,omitempty"`
+	// Username of your INWX account.
+	Username string `json:"username,omitempty"`
+
+	// Password of your INWX account.
+	Password string `json:"password,omitempty"`
+
+	// The shared secret is used to generate a TAN if you have activated "Mobile TAN" for your INWX account.
 	SharedSecret string `json:"shared_secret,omitempty"`
-	EndpointURL  string `json:"endpoint_url,omitempty"`
+
+	// URL of the JSON-RPC API endpoint. It defaults to the production endpoint.
+	EndpointURL string `json:"endpoint_url,omitempty"`
 
 	client   *client
 	clientMu sync.Mutex