Usage with Flask factory pattern?

Nobody has claimed this yet.

I wasn't able to find this in the docs, but what is the recommended way to use this library with the Flask factory pattern?

My approach was to initialize the Marshmallow object in my models file and then in `register_extensions` call `Marshmallow.init_app` like so:

```python
# models.py
from flask_marshmallow import Marshmallow
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()
ma = Marshmallow()
```

```python
def register_extensions(app: Flask):
db.init_app(app)
with app.app_context():
db.create_all()
db.session.commit()
ma.init_app(app)
```

Is this the recommended approach? It seems to work while trying it out from the flask shell.

Review the factory-pattern example in the issue, especially models.py and register_extensions. Check the existing Flask integration documentation and comment thread first; done means the recommended initialization approach is decided and documented with a clear factory-pattern example.

Written by the indexing model from the issue text.