Update runs serializer and users model

[arsemagebremichael]

Description

This change updates the Run model serializer to ensure all relevant fields are returned, including nested related fields for input files and output artifacts. Additionally, the model's image field has been converted from ImageField to URLField.

This addresses issues around incomplete API responses where some model fields were missing. The use of URLField for images aligns with the approach to handle image references via URLs rather than local file uploads.

The motivation behind this change is to improve data accessibility for consumers of the API and simplify image handling logic.

Dependencies: None

Fixes # (issue) [Insert related Jira or issue link if available]

Type of change

• Improvement
• Bug fix (non-breaking)
• New feature (non-breaking)
• Breaking change
• Documentation update
• Optimization

How Has This Been Tested?

• Manual verification of API responses returning all fields and nested serializers
• Automated tests for serializer correctness (if applicable)

Checklist:

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