[#101] Optimize GRAPPA calls, memoization, bug fixes batch

.env

docker-compose-services-shared.yml

package-lock.json

package.json

src/app.ts

src/cache/cache.ts

src/middleware/authorizationChecker.ts

src/models/authorization-bag.ts

src/models/cern-authorization-service.ts

src/models/cern-oauth.ts

src/models/channel-helpers.ts

src/models/channel.ts

src/models/notification.ts

src/models/preference.ts

src/models/tag.ts

src/models/user-channel-collection.ts

src/services/impl/channels/add-member-to-channel.ts

src/services/impl/channels/find-all-channels.ts

src/services/impl/channels/find-public-channels.ts

src/services/impl/channels/get-channel-groups.ts