Add HTTP client and login support

src/backend/client.rs

@@ -0,0 +1,31 @@
+use super::Backend;
+use anyhow::{anyhow, bail, Result};
+use isahc::http::StatusCode;
+use isahc::prelude::*;
+
+impl Backend {
+    /// Try to login a user with the provided credentials and return, wether the login suceeded.
+    pub async fn login(&self) -> Result<bool> {
+        let server_url = self.get_server_url().ok_or(anyhow!("No server URL set!"))?;
+        let data = self.get_login_data().ok_or(anyhow!("No login data set!"))?;
+
+        let request = Request::post(format!("{}/login", server_url))
+            .header("Content-Type", "application/json")
+            .body(serde_json::to_string(&data)?)?;
+
+        let mut response = isahc::send_async(request).await?;
+
+        let success = match response.status() {
+            StatusCode::OK => {
+                let token = response.text_async().await?;
+                self.set_token(&token);
+                println!("{}", &token);
+                true
+            }
+            StatusCode::UNAUTHORIZED => false,
+            _ => bail!("Unexpected response status!"),
+        };
+
+        Ok(success)
+    }
+}