Rust backend setup

backend/migrations/diesel_initial_setup/down.sql

@@ -0,0 +1,2 @@
+DROP FUNCTION IF EXISTS diesel_manage_updated_at(_tbl regclass);
+DROP FUNCTION IF EXISTS diesel_set_updated_at();

backend/migrations/diesel_initial_setup/up.sql

@@ -0,0 +1,18 @@
+CREATE OR REPLACE FUNCTION diesel_manage_updated_at(_tbl regclass) RETURNS VOID AS $$
+BEGIN
+    EXECUTE format('CREATE TRIGGER set_updated_at BEFORE UPDATE ON %s
+                    FOR EACH ROW EXECUTE PROCEDURE diesel_set_updated_at()', _tbl);
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE FUNCTION diesel_set_updated_at() RETURNS trigger AS $$
+BEGIN
+    IF (
+        NEW IS DISTINCT FROM OLD AND
+        NEW.updated_at IS NOT DISTINCT FROM OLD.updated_at
+    ) THEN
+        NEW.updated_at := current_timestamp;
+    END IF;
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;