TimeDispatcher/dispatcher/models.py

from django.db import models

class Parent(models.Model):
    project_num = models.CharField(max_length=32)
    name = models.CharField(max_length=256)

    def __str__(self):
        return self.name


class Project(models.Model):
    parent = models.ForeignKey(
        Parent,
        on_delete=models.CASCADE,
        null=True
    )
    name = models.CharField(max_length=256)

    def __str__(self):
        return self.name


class Task(models.Model):
    project = models.ForeignKey(Project, on_delete=models.CASCADE)
    date = models.DateField(null=False)
    duration = models.IntegerField(null=False, default=0)
    name = models.CharField(max_length=512, default="")

    class Meta:
        constraints = [
            models.UniqueConstraint(fields=["date", "project", "name"], name="unique_daily_task")
        ]