## Description
The changes in `sign-direct-template.tsx` automatically fill in field
values for text, number, and dropdown fields when default values are
present or if the fields are read-only. In `checkbox-field.tsx`, the
changes fix the checkbox signing by checking if the validation is met
and improving how it saves or removes checkbox choices.
## Testing Performed
I tested the code locally with a variety of documents/fields.
## Checklist
<!--- Please check the boxes that apply to this pull request. -->
<!--- You can add or remove items as needed. -->
- [x] I have tested these changes locally and they work as expected.
- [ ] I have added/updated tests that prove the effectiveness of these
changes.
- [ ] I have updated the documentation to reflect these changes, if
applicable.
- [x] I have followed the project's coding style guidelines.
- [ ] I have addressed the code review feedback from the previous
submission, if applicable.
Introduces the ability for users with the **Assistant** role to prefill
fields on behalf of other signers. Assistants can fill in various field
types such as text, checkboxes, dates, and more, streamlining the
document preparation process before it reaches the final signers.
