feat: added business models, implemented business signup and signin

solution/apps/core/apps.py

@@ -0,0 +1,6 @@
+from django.apps import AppConfig
+
+
+class CoreConfig(AppConfig):
+    name = "apps.core"
+    label = "core"

solution/apps/core/models.py

@@ -0,0 +1,23 @@
+import uuid
+
+from django.core.exceptions import ValidationError
+from django.db import models
+
+from config.errors import UniqueConstraintError
+
+
+class BaseModel(models.Model):
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+
+    class Meta:
+        abstract = True
+
+    def save(self, *args, **kwargs) -> None:  # noqa: ANN002, ANN003
+        self.full_clean(validate_unique=False)
+
+        try:
+            self.validate_unique()
+        except ValidationError as e:
+            raise UniqueConstraintError(e) from None
+
+        super().save(*args, **kwargs)