Improve performance when retrieving a project with collaborators

[Brend-Smits]

Description

Add Collaborators by performing for each loop instead of joining tables. Joining tables by using Include() caused the query to take sometimes up to 10 times as long. This was an issue as it caused a drastic slow down when retrieving all projects, retrieving project detail, or when searching for projects.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• 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

Checklist

• My code follows the style guidelines of this project
• I did not update API Controllers, if I did, I added/changed Postman tests
• 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
• 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
• I updated the changelog with an end-user readable description
• I assigned this pull request to the correct project board to update the sprint board

Steps to Test or Reproduce

Outline the steps to test or reproduce the PR here.
These steps will be used during release testing.

1. Go to the project overview page
2. Check if it's snappy and more performance compared to on staging

Link to issue

Closes: #331

[waltersajtos]

Solution works, looks good to me