Improve Factory Model and Add Slug Trait

[Najmul-Hasan-Sobuj]

Description:

• Factory Model Update: Updated the factory for the model to ensure user_id is properly assigned by directly creating a user instance and associating its ID. This resolves the issue where user_id was not being inserted as expected.

• Slug Trait: Created a reusable Slug trait for generating unique slugs, enhancing consistency across models that require slugs. This trait can be applied to any model where a slug is needed, helping to keep the codebase clean and DRY.

Changes:

• Modified Factory to use User::factory()->create()->id for user_id assignment.
• Added Slug trait for consistent slug generation.

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