feat: use custom type to handle existing naive datetimes

app/portal/pool.py

@@ -2,15 +2,16 @@ import logging
 import secrets
 from datetime import datetime, timezone
 
-from flask import render_template, url_for, flash, redirect, Response, Blueprint
+import sqlalchemy
+from flask import (Blueprint, Response, flash, redirect, render_template,
+                   url_for)
 from flask.typing import ResponseReturnValue
 from flask_wtf import FlaskForm
-import sqlalchemy
-from wtforms import StringField, SubmitField, SelectField
+from wtforms import SelectField, StringField, SubmitField
 from wtforms.validators import DataRequired
 
 from app.extensions import db
-from app.models.base import Pool, Group
+from app.models.base import Group, Pool
 from app.portal.util import LifecycleForm
 
 bp = Blueprint("pool", __name__)