refacto: use structure default _id

src/app/form/form.component.html

src/app/form/form.component.ts

src/app/home/home.component.ts

src/app/map/components/map.component.ts

src/app/map/services/map.service.ts

src/app/models/structure.model.ts

src/app/models/user.model.ts

src/app/profile/services/profile.service.ts

src/app/services/structure.service.ts

...onents/structure-details/structure-details.component.html

...mponents/structure-details/structure-details.component.ts

src/app/structure-list/structure-list.component.ts