feat: create, publish, import and report on quizzes over MCP

- quizzes_create_quiz, update_quiz, delete_quiz (confirm repeats the
  slug), publish, unpublish, import_quiz (the existing import route) and
  quiz_stats on new manage routes
- stats close expired open test attempts first, then report per student
  over completed whole-quiz attempts and per question over every
  completed attempt
- input is checked before the database; TestManageAPIAgainstDatabase is
  written and skipped under -short

controllers/api/manage_json.go

@@ -114,3 +114,78 @@ func managedQuestion(q models.Question) managedQuestionJSON {
 	}
 	return out
 }
+
+type statsJSON struct {
+	Quiz      statsQuizJSON      `json:"quiz"`
+	Students  []studentStatJSON  `json:"students"`
+	Questions []questionStatJSON `json:"questions"`
+}
+
+type statsQuizJSON struct {
+	ID            uint   `json:"id"`
+	Slug          string `json:"slug"`
+	Title         string `json:"title"`
+	Mode          string `json:"mode"`
+	PassingScore  int    `json:"passing_score"`
+	QuestionCount int    `json:"question_count"`
+}
+
+type studentStatJSON struct {
+	UserID           uint       `json:"user_id"`
+	Email            string     `json:"email"`
+	Name             *string    `json:"name"`
+	Surname          *string    `json:"surname"`
+	Attempts         int        `json:"attempts"`
+	BestScorePercent *float64   `json:"best_score_percent"`
+	LastScorePercent *float64   `json:"last_score_percent"`
+	LastCompletedAt  *wire.Time `json:"last_completed_at"`
+	Passed           bool       `json:"passed"`
+}
+
+type questionStatJSON struct {
+	ID              uint             `json:"id"`
+	Text            string           `json:"text"`
+	Type            string           `json:"type"`
+	Answered        int              `json:"answered"`
+	Correct         int              `json:"correct"`
+	CorrectPercent  *float64         `json:"correct_percent"`
+	MostChosenWrong *wrongAnswerJSON `json:"most_chosen_wrong"`
+}
+
+type wrongAnswerJSON struct {
+	AnswerID uint   `json:"answer_id"`
+	Text     string `json:"text"`
+	Count    int    `json:"count"`
+}
+
+func quizStats(s *classes.Stats) statsJSON {
+	out := statsJSON{
+		Quiz: statsQuizJSON{
+			ID: s.Quiz.ID, Slug: s.Quiz.Slug, Title: s.Quiz.Title, Mode: quizMode(&s.Quiz),
+			PassingScore: s.Quiz.PassingScore, QuestionCount: s.QuestionCount,
+		},
+		Students:  make([]studentStatJSON, 0, len(s.Students)),
+		Questions: make([]questionStatJSON, 0, len(s.Questions)),
+	}
+	for _, st := range s.Students {
+		row := studentStatJSON{
+			UserID: st.UserID, Email: st.Email, Name: st.Name, Surname: st.Surname, Attempts: st.Attempts,
+			BestScorePercent: st.BestScorePercent, LastScorePercent: st.LastScorePercent, Passed: st.Passed,
+		}
+		if st.LastCompletedAt != nil {
+			t := wireTime(*st.LastCompletedAt)
+			row.LastCompletedAt = &t
+		}
+		out.Students = append(out.Students, row)
+	}
+	for _, q := range s.Questions {
+		row := questionStatJSON{
+			ID: q.ID, Text: q.Text, Type: q.Type, Answered: q.Answered, Correct: q.Correct, CorrectPercent: q.CorrectPercent,
+		}
+		if q.MostChosenWrong != nil {
+			row.MostChosenWrong = &wrongAnswerJSON{AnswerID: q.MostChosenWrong.AnswerID, Text: q.MostChosenWrong.Text, Count: q.MostChosenWrong.Count}
+		}
+		out.Questions = append(out.Questions, row)
+	}
+	return out
+}