Filter categories

[niraymak]

Is your feature request related to a problem? Please describe.
It should be possible to filter through categories.

Describe the solution you'd like
Implement a way to filter on categories. The endpoint should be able to return all projects with one or more categories depending on the ones selected.

If possible please reuse this endpoint: https://github.com/DigitalExcellence/dex-backend/blob/develop/API/Controllers/ProjectController.cs#L160

Production URL
https://dex.software/project/overview

Additional context

[waltersajtos]

Also change the getAllCategories endpoint to public.

[waltersajtos]

Probably also a good idea to get the naming consistent for the Category recourses.

public class ProjectCategoryResource
    {

        /// <summary>
        ///     Gets or sets the Id of the category.
        /// </summary>
        public int CategoryId { get; set; }
    }

	public class ProjectCategoryResourceResult
    {

        /// <summary>
        ///     Gets or sets the Id of the project category.
        /// </summary>
        public int Id { get; set; }

        /// <summary>
        ///     Gets or sets the Name of the project category.
        /// </summary>
        public string Name { get; set; }

    }