Add some diagrams for the services and reorganization the services doc

docs/assets/changelog-service.png

docs/assets/credits-service.png

docs/assets/media-library-service.png

docs/components/custom-apps/admin-gui.md

docs/components/services/authentication.md

docs/components/services/changelog.md

docs/components/services/credits.md

docs/components/services/mailer.md

docs/components/services/media-library.md

docs/components/services/organizations.md

docs/components/services/resources-helper.md

docs/components/services/reuses.md

docs/components/services/social-media-share-helper.md

docs/miscellaneous/nestjs-micro-services.md