Add config extension module

Better way to parse environment variables and pass around config vars.

src/config.rs

@@ -0,0 +1,25 @@
+use anyhow::{Context, Result};
+
+#[derive(Clone, Debug)]
+pub struct Config {
+    pub database_url: String,
+    pub database_max_connections: u32,
+    pub host: String,
+    pub port: u16,
+}
+
+impl Config {
+    pub fn new() -> Result<Config> {
+        let database_url = std::env::var("DATABASE_URL").context("DATABASE_URL not set")?;
+        let database_max_connections = std::env::var("DATABASE_MAX_CONNECTIONS").context("DATABASE_MAX_CONNECTIONS not set")?.parse()?;
+        let host = std::env::var("HOST").context("HOST not set")?;
+        let port = std::env::var("PORT").context("PORT not set")?.parse()?;
+
+        Ok(Config {
+            database_url,
+            database_max_connections,
+            host,
+            port,
+        })
+    }
+}