refactor: structure of an hexagonal architecture

Created a kernel crate to store models and future action implementations.
Will be useful to create admin cli.

lib/admin_cli/src/main.rs

@@ -0,0 +1,6 @@
+use anyhow::Result;
+
+fn main() -> Result<()> {
+    println!("Starting minauthator admin CLI");
+    Ok(())
+}