Write auth key to file

This commit allows us to now write the auth key to the proper file.
After writing and restarting tsdproxy everything seems to be getting
picked up and is working successfully.

src/lib.rs

@@ -1,5 +1,6 @@
 use std::error::Error;
-use std::fs::read_to_string;
+use std::fs::{read_to_string, File};
+use std::io::Write;
 
 use oauth2::basic::BasicClient;
 use oauth2::reqwest::http_client;
@@ -9,16 +10,23 @@ mod types;
 use types::{AuthKeyRequest, AuthKeyResponse, ClientAuth};
 
 pub fn run() -> Result<(), Box<dyn Error>> {
+    println!("Reading Client ID And Secret From File");
     let client_auth = read_client_auth()?;
 
-    println!("Client ID: {}", client_auth.id);
-    println!("Client Secret: {}", client_auth.secret);
-
+    println!("Getting API Token With Client ID: {}", client_auth.id);
     let access_token = get_api_token(client_auth.id, client_auth.secret)?;
 
+    println!("Generating New Auth Key");
     let auth_key = get_auth_key(access_token)?;
 
-    println!("Auth Key: {}", auth_key);
+    println!("Writing Auth Key to File");
+    write_auth_key(auth_key)?;
+
+    println!(
+        "Auth key has been successfully updated.\n
+*** Make sure in your tsdproxy config you are pointing to the file '/config/.auth-key' to pick up the key. ***
+*** Make sure you restart tsdproxy for the new keys to be used ***"
+    );
 
     Ok(())
 }
@@ -81,3 +89,11 @@ fn get_auth_key(api_token: AccessToken) -> Result<String, Box<dyn Error>> {
 
     Ok(auth_response.get_auth_key())
 }
+
+fn write_auth_key(auth_key: String) -> Result<(), Box<dyn Error>> {
+    let mut keyfile = File::create("config/.auth-key")?;
+
+    keyfile.write_all(auth_key.as_bytes())?;
+
+    Ok(())
+}