Solid-backend

- New Quiz type Ranking, Range and True/False
- Custom admin input for QuizQuestion
- Validation of QuizQuestion upon creation
- QuizAnswers are shuffled before Response
- Quiz Tags now use taggit
- New quizmeta Endpoint to provide metadata of the existing QuizQuestions
- New quizsession Endpoint to accept "tags", "difficulty" and "count" which provides a set of Quizanswers
- Quiz now uses MediaObject for Images.

*****************************
- Correct Typo which caused problems during schema generation for MDTextFields

*****************************
- Add drf-spectacular schema postprocessing hook for ChoiceFields

*****************************
- Fix declaration of MDTextField and related drf-spectacular detection

*****************************
- Add TitleSerializerExtension

*****************************

- Add drf-spectacular as optional dependecy
- Add drf-spectacular field extension for mdstring format strings
- Add SolidModelSerializer