feat: config crate with legacy env names

crates/config/src/database_config.rs

@@ -0,0 +1,16 @@
+use std::fmt;
+
+use serde::Deserialize;
+
+#[derive(Clone, Deserialize)]
+pub struct DatabaseConfig {
+    pub url: String,
+}
+
+impl fmt::Debug for DatabaseConfig {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("DatabaseConfig")
+            .field("url", &"<redacted>")
+            .finish()
+    }
+}