implement test changes regarding database

also added .env for database connection details (used by sqlx)

src/configuration.rs

@@ -22,4 +22,13 @@ pub fn get_configuration() -> Result<Settings, config::ConfigError> {
 
     // Try convert into Settings type
     settings.try_into()
+}
+
+impl DatabaseSettings {
+    pub fn connection_string(&self) -> String {
+        format!(
+            "postgres://{}:{}@{}:{}/{}",
+            self.username, self.password, self.host, self.port, self.database_name    
+        )
+    }
 }