feat: Implement `BlankQuestionViewModel`

[apomalyn]

Requirements

Implement a BlankQuestion model extending TextQuestion.

Implement a BlankViewModel that:

• extends TextQuestionViewModel
• have
  • List<String> blanksToFill: list of the blanks filled by the user, only used when useKeyboard is true
  • void onBlankValueChange(String value, int index): update blanksToFill for a certain index.
• override:
  • isSubmitEnabled
  • onSubmitPressed: inject in the subject the answer selected by the user then validate the answer before calling the right result flow.

What needs to be done

Implement under practices/questions/models, a BlankQuestion model extending TextQuestion:

• format: QuestionFormats.blank

Implement under practices/questions, a view model BlankQuestionViewModel:

• extending TextQuestionViewModel
• constructor:
  • everything TextQuestionViewModel needs,
  • instead of a TextQuestion, requires a BlankQuestion
  • initialize blanksToFill based on question.subject (quantity of _)
• implement:
  • void onBlankValueChange(String value, int index): it should do blanksToFill[index] = value
• override:
  • isSubmitEnabled: should be true if selectedOptionsIndexes size equals blanksToFill length or all blanksToFill values aren't empty.
  • onSubmitPressed:
  • replace all question.subject, _ by the corresponding answer, from selectedOptionsIndexes or blanksToFill based on useKeyboard
  • test the newly built answer against question.allowedAnswers[0]
  • if valid call _onSuccess otherwise _onFailure

Dependencies

Child of #192

Depends on:

• 189