Keep progranm from crashing when webhook_url is not provided

- Also require webhook_url to be a valid Url

packages/jobboerse/src/server_config.rs

@@ -37,7 +37,8 @@ pub(crate) struct ProgramConfig {
     pub(crate) login_provider: LoginProviderConfig,
     #[serde(skip_serializing_if = "Option::is_none", default)]
     pub(crate) email: Option<EmailConfig>,
-    pub(crate) webhook_url: Option<String>,
+    #[serde(default)]
+    pub(crate) webhook_url: Option<Url>,
 }
 
 #[derive(Serialize, Deserialize, Debug)]

packages/jobboerse/src/webhook.rs

@@ -18,7 +18,7 @@ pub(crate) struct NewOfferWebhookData {
 
 pub(crate) async fn send_new_offer_message(
     hb: &Handlebars<'_>,
-    webhook_url: String,
+    webhook_url: Url,
     data: &NewOfferWebhookData,
 ) -> Result<bool, RenderError> {
     let message_text = hb.render(template::WEBHOOK_NEW_OFFER_MESSAGE, data)?;
@@ -39,7 +39,7 @@ pub(crate) async fn send_new_offer_message(
     let arc = Arc::new(tls_config);
     let connector = Connector::new().rustls(arc);
     let client = Client::builder().connector(connector).finish();
-    let request_result = client.post(webhook_url).send_json(&msg).await;
+    let request_result = client.post(webhook_url.as_str()).send_json(&msg).await;
     let success = match request_result {
         Ok(response) => {
             debug!(