feat: Add collaborators.all

[baptmaury]

Add get /collaborators endpoint with Collaborators.all
Introduce ExtendedCollaborator interface

Done in pair with @TheoPouletSouchard

Used in https://github.com/Scalingo/dashboard-next/pull/1748

[notion-workspace]

List collaborators of all my apps

[aurelien-reeves-scalingo]

Would it be possible to use optional properties?

Also, could we craft the API endpoint for it to return the actual username and email of the registered user when the user has accepted the invite?

Thus, we would not need a new "extended" interface

export interface Collaborator {
  /** Id of the collaborator */
  id: string;
  /** Email of the collaborator to invite */
  email: string;
  /** Unique User ID of the user who accepted the collaboration */
  user_id: string;
  /** ID of the application owning the collaborator */
  app_id: string;
  /** Username of the person to invite */
  username: string;
  /** Status of the invitation */
  status: string;
  /** Name of the app */
  app_name?: string;
}

[baptmaury]

I already implemented it locally :)