/// <summary>
        /// Updates a workflowelement in a project.
        /// </summary>
        /// <param name="projectId"></param>
        /// <param name="categoryId"></param>
        /// <param name="workflowElement"></param>
        /// <returns></returns>
        public ProjectModel Put(string projectId, string categoryId, WorkflowElement workflowElement)
        {
            var project  = Get(projectId);
            var category = project.WorkflowElementCategories.First(x => x.CategoryId == categoryId);
            var element  = category.WorkflowElements.First(x => x.ElementId == workflowElement.ElementId);

            element.Explanation = workflowElement.Explanation;
            element.IsDone      = workflowElement.IsDone;
            element.IsRelevant  = workflowElement.IsRelevant;
            element.Description = workflowElement.Description;

            var newProject = ProjectsCollection.ReplaceOne(x => x.Id == projectId, project);

            return(project);
        }