Add categories to project metadata overview

[ewan-escience]

Add categories to project metadata overview

Changes proposed in this pull request

• Add categories to project metadata overview, it counts assigned incidental leaf nodes (nodes that can have children but of which no child is assigned to the project)

How to test

• docker compose down --volumes && docker compose build --parallel && docker compose up --scale data-generation=1
• Sign in as admin, look at the project metadata overview, the final columns should show the category count
• Create a new project, add an organisation with categories to it and assign one category to the project
• When saving the category, you will see that all parents are also saved in the dev tools of your browser (F12, network tab), but in the project metadata overview, it should be counted as one (this should also be the case whan assigning a category that does have children, but of which you don't assign any children)
• Check for other project pages if the category count makes sense

closes #1596

PR Checklist:

• Increase version numbers in docker-compose.yml
• Link to a GitHub issue
• Update documentation
• Tests

[sonarqubecloud]

Quality Gate passed for 'rsd-database'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqubecloud]

Quality Gate passed for 'rsd-frontend'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[jmaassen]

Works as expected