Generate API Token

Wrote function that generates a tailscale API token from our client id
and client secret values that we have. Have checked with the logs on
tailscale and can see that it is indeed generating the keys. This can be
considered a solution to issue #6.

src/lib.rs

@@ -1,20 +1,31 @@
 use std::error::Error;
 use std::fs::read_to_string;
 
+use oauth2::basic::BasicClient;
+use oauth2::reqwest::http_client;
+use oauth2::AccessToken;
+use oauth2::AuthUrl;
+use oauth2::ClientId;
+use oauth2::ClientSecret;
+use oauth2::TokenResponse;
+use oauth2::TokenUrl;
+
+mod types;
+use types::ClientAuth;
+
 pub fn run() -> Result<(), Box<dyn Error>> {
     let client_auth = read_client_auth()?;
 
-    println!("Client ID: {}", client_auth.client_id);
-    println!("Client Secret: {}", client_auth.client_secret);
+    println!("Client ID: {}", client_auth.id);
+    println!("Client Secret: {}", client_auth.secret);
+
+    let access_token = get_api_token(client_auth.id, client_auth.secret)?;
+
+    println!("Access Token: {access_token:#?}");
 
     Ok(())
 }
 
-struct ClientAuth {
-    client_id: String,
-    client_secret: String,
-}
-
 fn read_client_auth() -> Result<ClientAuth, Box<dyn Error>> {
     let mut id = String::new();
     let mut secret = String::new();
@@ -29,8 +40,22 @@ fn read_client_auth() -> Result<ClientAuth, Box<dyn Error>> {
         }
     }
 
-    Ok(ClientAuth {
-        client_id: id,
-        client_secret: secret,
-    })
+    Ok(ClientAuth { id, secret })
+}
+
+fn get_api_token(client_id: String, client_secret: String) -> Result<AccessToken, Box<dyn Error>> {
+    let client = BasicClient::new(
+        ClientId::new(client_id),
+        Some(ClientSecret::new(client_secret)),
+        AuthUrl::new("https://api.tailscale.com/api/v2/oauth/token".to_string())?,
+        Some(TokenUrl::new(
+            "https://api.tailscale.com/api/v2/oauth/token".to_string(),
+        )?),
+    );
+
+    let token_result = client.exchange_client_credentials().request(http_client)?;
+
+    let access_token = token_result.access_token().to_owned();
+
+    Ok(access_token)
 }

src/types.rs

@@ -0,0 +1,4 @@
+pub struct ClientAuth {
+    pub id: String,
+    pub secret: String,
+}