feat: prepare backend for post exercise overview

### Additions

* added `InjectInterface` interface
* added field `name: String!` to `TInjectType` type
* added `EmailAddressInterface` interface and corresponding types
* added `LearningObjectiveInterface` and corresponding types
* added `LearningActivityInterface` and corresponding types
* added `TeamLearningObjectiveInterface` and corresponding types
* added `TeamLearningActivityInterface` and corresponding types
* added field `showOverview: Boolean!` to `TeamType` type
* added mutation `enablePostExerciseOverview(teamIds: [ID!]!, enable: Boolean! = True): [TeamType!]!`

### Changes

* field `definition: DefinitionType!` on `QuestionnaireType` changed to `definition: ExerciseDefinitionType!`
* field `activity: LearningActivityType!` on `IToolType` changed to `activity: ILearningActivityType!`
* field `activity: LearningActivityType!` on `IInjectType` changed to `activity: ILearningActivityType!`
* changed query `teamLearningObjectives(teamIds: [ID!]!): [TeamLearningObjectiveType!]!` to `teamLearningObjectives(teamIds: [ID!]!): [TeamLearningObjectiveInterface!]!`
* query `teamLearningObjectives` can now be used by trainees

### Deletions

* removed `LearningObjectiveType` type
* removed `LearningActivityType` type

Closes #492