Error when the URL scheme doesn't match the database type

src/config.rs

@@ -366,6 +366,26 @@ make_config! {
 }
 
 fn validate_config(cfg: &ConfigItems) -> Result<(), Error> {
+    let db_url = cfg.database_url.to_lowercase();
+    
+    if cfg!(feature = "sqlite") {
+        if db_url.starts_with("mysql:") || db_url.starts_with("postgresql:") {
+            err!("`DATABASE_URL` is meant for MySQL or Postgres, while this server is meant for SQLite")
+        }
+    }
+
+    if cfg!(feature = "mysql") {
+        if !db_url.starts_with("mysql:") {
+            err!("`DATABASE_URL` should start with mysql: when using the MySQL server")
+        }
+    }
+
+    if cfg!(feature = "postgresql") {
+        if !db_url.starts_with("postgresql:") {
+            err!("`DATABASE_URL` should start with postgresql: when using the PostgreSQL server")
+        }
+    }
+
     if let Some(ref token) = cfg.admin_token {
         if token.trim().is_empty() {
             err!("`ADMIN_TOKEN` is enabled but has an empty value. To enable the admin page without token, use `DISABLE_ADMIN_TOKEN`")