feat: Add branding and configuration for connectors

api/assets/engines/datashield/favicon.ico

api/assets/engines/datashield/logo_small.png

api/assets/engines/default/custom.css

api/assets/engines/default/favicon.ico

api/assets/engines/default/favicon.png

api/assets/engines/default/login.md

api/assets/engines/default/logo.png

api/assets/engines/default/logo_small.png

api/assets/engines/default/tos.md

api/package-lock.json

api/package.json

api/src/engine/assets.service.ts

api/src/engine/connectors/datashield/assets/SOPHIA_logo.png

api/src/engine/connectors/datashield/main.connector.ts

api/src/engine/connectors/exareme/main.connector.ts

api/src/engine/engine.controller.ts

api/src/engine/engine.interfaces.ts

api/src/engine/engine.module.ts

api/src/engine/engine.resolver.ts

api/src/engine/models/configuration.model.ts