[BUG] ModelSchema does not validate Blank fields properly

[jam13]

Describe the bug
Given a model field:

description = models.TextField(blank=True)

ModelSchema treats it as an optional field (which is I guess correct), but doesn't default it to an empty string. This results in integrity errors when trying to save to the db.

Excluding the field from model_fields and explicitly declaring it as:

project_description: str = ""

is a workaround.

From what I understand, Django encourages the use of blank without null for text fields to avoid a mix of empty values.

Versions (please complete the following information):

• Python version: 3.11
• Django version: 4.2
• Django-Ninja version: 1.0b2
• Pydantic version: 2.4

[michalwerner]

I also stumbled upon this issue.
The fix seems to be simple but I'm not sure if it won't result in other issues or if and if so why this was intentional.
See draft PR: #1374