feat: registrationBegin method without email;

fix: missing sqlc query parameter name;
feat: util for generating security codes;
feat: enums package

sqlc/sqlc.yaml

@@ -8,7 +8,7 @@ sql:
       out: "../backend/internal/database"
       sql_package: "pgx/v5"
       emit_prepared_queries: true
-      emit_interface: false
+      emit_pointers_for_null_types: true
   database:
     # managed: true
     uri: "postgresql://postgres:postgres@localhost:5432/postgres?sslmode=disable"