Create Store service for updating the UI automatically

[DavMunHer]

Given all the refactors made in the PR #19 , when we start implementing the backend API, we will be needing a new service (Store Service) that will consume from the project api service.

Example of code implementation (this is just an example and will not work in the project, since our entities are a bit different):

@Injectable({ providedIn: 'root' })
export class ProjectStore {
  private _project = signal<Project | null>(null);
  private _sections = signal<Record<string, Section>>({});
  private _tasks = signal<Record<string, Task>>({});

  readonly projectView = computed<ProjectView | null>(() => {
    const project = this._project();
    if (!project) return null;

    return {
      id: project.id,
      name: project.name,
      sections: project.sectionIds
        .map(id => this._sections()[id])
        .filter(Boolean)
        .map(section => ({
          id: section.id,
          title: section.title,
          tasks: section.taskIds
            .map(id => this._tasks()[id])
            .filter(Boolean)
            .map(task => ({
              id: task.id,
              title: task.title,
              completed: task.completed,
            })),
        })),
    };
  });

  constructor(private projectApi: ProjectApi) {}

  loadProject(projectId: string) {
    this.projectApi.loadProject(projectId).subscribe(({ project, sections, tasks }) => {
      this._project.set(project);
      this._sections.set(Object.fromEntries(sections.map(s => [s.id, s])));
      this._tasks.set(Object.fromEntries(tasks.map(t => [t.id, t])));
    });
  }
}

For the component itself:

export class ProjectViewComponent implements OnInit {
  readonly project = this.projectStore.projectView;

  constructor(private projectStore: ProjectStore) {}

  ngOnInit() {
    this.projectStore.loadProject('123'); // trigger HTTP request
  }
}

[DavMunHer]

Issue solved when refactoring project in PR #25