Fix authenticator docs

Author: alexeyzimarev

docs/authenticators.md

@@ -1,15 +1,36 @@
 # Authenticators
 
-RestSharp includes authenticators for basic HTTP (Authorization header), 
-NTLM and parameter-based systems. 
+RestSharp includes authenticators for basic HTTP, OAuth1 and token-based (JWT and OAuth2). 
+
+There are two ways to set the authenticator: client-wide or per-request.
+
+Set the client-wide authenticator by assigning the `Authenticator` property of `RestClientOptions`:
+
+```csharp
+var options = new RestClientOptions("http://example.com") {
+    Authenticator = new HttpBasicAuthenticator("username", "password")
+};
+var client = new RestClient(options);
+```
+
+To set the authenticator per-request, assign the `Authenticator` property of `RestRequest`:
+
+```csharp
+var request = new RestRequest("/api/users/me") {
+    Authenticator = new HttpBasicAuthenticator("username", "password")
+};
+var response = await client.ExecuteAsync(request, cancellationToken);
+```
 
 ## Basic Authentication
 
 The `HttpBasicAuthenticator` allows you pass a username and password as a basic `Authorization` header using a base64 encoded string.
 
 ```csharp
-var client = new RestClient("http://example.com");
-client.Authenticator = new HttpBasicAuthenticator("username", "password");
+var options = new RestClientOptions("http://example.com") {
+    Authenticator = new HttpBasicAuthenticator("username", "password")
+};
+var client = new RestClient(options);
 ```
 
 ## OAuth1
@@ -21,23 +42,29 @@ For OAuth1 authentication the `OAuth1Authenticator` class provides static method
 This method requires a `consumerKey` and `consumerSecret` to authenticate.
 
 ```csharp
-var client = new RestClient("http://example.com");
-client.Authenticator = OAuth1Authenticator.ForRequestToken(consumerKey, consumerSecret);
+var options = new RestClientOptions("http://example.com") {
+    Authenticator = OAuth1Authenticator.ForRequestToken(consumerKey, consumerSecret)
+};
+var client = new RestClient(options);
 ```
 
 ### Access token
 
 This method retrieves an access token when provided `consumerKey`, `consumerSecret`, `oauthToken`, and `oauthTokenSecret`.
 
 ```csharp
-client.Authenticator = OAuth1Authenticator.ForAccessToken(
+var authenticator = OAuth1Authenticator.ForAccessToken(
     consumerKey, consumerSecret, oauthToken, oauthTokenSecret
 );
+var options = new RestClientOptions("http://example.com") {
+    Authenticator = authenticator
+};
+var client = new RestClient(options);
 ```
 
 This method also includes an optional parameter to specify the `OAuthSignatureMethod`.
 ```csharp
-client.Authenticator = OAuth1Authenticator.ForAccessToken(
+var authenticator = OAuth1Authenticator.ForAccessToken(
     consumerKey, consumerSecret, oauthToken, oauthTokenSecret, 
     OAuthSignatureMethod.PlainText
 );
@@ -48,7 +75,7 @@ client.Authenticator = OAuth1Authenticator.ForAccessToken(
 The same access token authenticator can be used in 0-legged OAuth scenarios by providing `null` for the `consumerSecret`.
 
 ```csharp
-client.Authenticator = OAuth1Authenticator.ForAccessToken(
+var authenticator = OAuth1Authenticator.ForAccessToken(
     consumerKey, null, oauthToken, oauthTokenSecret
 );
 ```
@@ -64,9 +91,13 @@ RestSharp has two very simple authenticators to send the access token as part of
 For example:
 
 ```csharp
-client.Authenticator = new OAuth2AuthorizationRequestHeaderAuthenticator(
+var authenticator = new OAuth2AuthorizationRequestHeaderAuthenticator(
     token, "Bearer"
 );
+var options = new RestClientOptions("http://example.com") {
+    Authenticator = authenticator
+};
+var client = new RestClient(options);
 ```
 
 The code above will tell RestSharp to send the bearer token with each request as a header. Essentially, the code above does the same as the sample for `JwtAuthenticator` below.
@@ -79,6 +110,10 @@ The JWT authentication can be supported by using `JwtAuthenticator`. It is a ver
 
 ```csharp
 var authenticator = new JwtAuthenticator(myToken);
+var options = new RestClientOptions("http://example.com") {
+    Authenticator = authenticator
+};
+var client = new RestClient(options);
 ```
 
 For each request, it will add an `Authorization` header with the value `Bearer <your token>`.
@@ -91,10 +126,14 @@ You can write your own implementation by implementing `IAuthenticator` and
 registering it with your RestClient:
 
 ```csharp
-var client = new RestClient();
-client.Authenticator = new SuperAuthenticator(); // implements IAuthenticator
+var authenticator = new SuperAuthenticator(); // implements IAuthenticator
+var options = new RestClientOptions("http://example.com") {
+    Authenticator = authenticator
+};
+var client = new RestClient(options);
 ```
 
-The `Authenticate` method is the very first thing called upon calling `RestClient.Execute` or `RestClient.Execute<T>`. The `Authenticate` method is passed the `RestRequest` currently being executed giving you access to  every part of the request data (headers, parameters, etc.)
+The `Authenticate` method is the very first thing called upon calling `RestClient.Execute` or `RestClient.Execute<T>`. 
+It gets the `RestRequest` currently being executed giving you access to  every part of the request data (headers, parameters, etc.)
 
 You can find an example of a custom authenticator that fetches and uses an OAuth2 bearer token [here](usage.md#authenticator).

docs/v107/README.md

@@ -65,7 +65,7 @@ request.AddHeader("Content-Type", "application/json");
 request.AddHeader("Accept", "application/json");
 ```
 
-This is completely unnecessary, and often harmful. The `Content-Type` header is the content header, not the request header. It might be different per individual part of the body when using multipart-form data, for example. RestSharp sets the correct content-type header automatically, based on your body format, so don't override it.
+This is **completely unnecessary**, and often harmful. The `Content-Type` header is the content header, not the request header. It might be different per individual part of the body when using multipart-form data, for example. RestSharp sets the correct content-type header automatically, based on your body format, so don't override it.
 The `Accept` header is set by RestSharp automatically based on registered serializers. By default, both XML and JSON are supported. Only change the `Accept` header if you need something else, like binary streams, or plain text.
 
 ### Making requests

src/RestSharp/RestClient.Extensions.cs

@@ -102,9 +102,6 @@ public static async Task<RestResponse<T>> ExecuteAsync<T>(
         RestRequest       request,
         CancellationToken cancellationToken = default
     ) {
-        if (request == null)
-            throw new ArgumentNullException(nameof(request));
-
         var response = await client.ExecuteAsync(request, cancellationToken).ConfigureAwait(false);
         return client.Serializers.Deserialize<T>(request, response, client.Options);
     }