feat: initial db persistence

src/main/resources/db/migration/V001__add_update_and_create_timestamp_triggers.sql

@@ -0,0 +1,18 @@
+create or replace function handle_timestamps()
+    returns trigger as
+$$
+begin
+    if lower(tg_op) = 'insert' then
+        new.created_at = coalesce(new.created_at, current_timestamp);
+        new.updated_at = coalesce(new.updated_at, current_timestamp);
+    elsif lower(tg_op) = 'update' then
+        if new.created_at is distinct from old.created_at then
+            raise exception 'Direct modification of created_at is not allowed.';
+        end if;
+
+        new.updated_at = current_timestamp;
+    end if;
+
+    return new;
+end;
+$$ language plpgsql;

src/main/resources/db/migration/V002__add_message_table.sql

@@ -0,0 +1,13 @@
+create table message (
+    id uuid not null primary key,
+    author varchar(31) not null,
+    content varchar(255) not null,
+
+    created_at timestamptz not null default current_timestamp,
+    updated_at timestamptz
+);
+
+create trigger handle_message_timestamps
+    before insert or update on message
+    for each row
+    execute function handle_timestamps();