add unique slug generator for stori title

[raykipkorir]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context. List any dependencies that are required for this change.

• I have added a unique slug generator which generates a unique slug when a stori is created with a title that already exists. If the title exists we slugify the title then append a random string to the slug.

Fixes # (issue) No fixes

Type of change

Please delete options that are not relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

• I have run the existing unit tests which have passed successfully.

Test Configuration:

          python manage.py migrate
          python manage.py test

Checklist:

• [X] My code follows the style guidelines of this project
• [X] I have performed a self-review of my code
• [X] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [X] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [X] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules