feat: add more links to learning activities

### Additions

* added field `injects: [DefinitionInjectType!]!` to `LearningActivityType` type
* added field `questionnaires: [QuestionnaireType!]!` to `LearningActivityType` type
* added field `tools: [ExtendedToolType!]!` to `LearningActivityType` type
* added field `addresses: [EmailAddressType!]!` to `LearningActivityType` type
* added field `activity: LearningActivityType` to `DefinitionInjectType` type
* added field `activity: LearningActivityType` to `QuestionnaireType` type
* added field `activity: LearningActivityType` to `ExtendedToolType` type
* added field `activity: LearningActivityType` to `EmailAddressType` type

Closes #415