Extract some functions to the app module: preparation for integration tests.

backend/src/lib.rs

@@ -0,0 +1,14 @@
+pub mod app;
+pub mod config;
+pub mod consts;
+pub mod data;
+pub mod log;
+
+mod email;
+mod hash;
+mod html_templates;
+mod ron_extractor;
+mod ron_utils;
+mod services;
+mod translation;
+mod utils;