[#230] Short URL implementation

.env

README.md

src/app-data-source.ts

src/controllers/channels/dto.ts

src/models/cern-authorization-service.ts

src/models/channel.ts

src/services/impl/channels/create-channel.ts

src/services/impl/channels/delete-channel.ts

src/services/impl/channels/manage-short-url.ts

src/services/impl/channels/update-channel.ts

src/services/impl/notifications/send-notification.ts

src/utils/fetch.ts