feat: localize interview questions (ko/en), send X-Lang header

internal/httpapi/diagnostic.go

@@ -13,6 +13,7 @@ type createDiagnosticSessionRequest struct {
 	TargetRole        string   `json:"target_role"`
 	Stack             []string `json:"stack"`
 	InterviewTimeline string   `json:"interview_timeline"`
+	Lang              string   `json:"lang"`
 }
 
 type submitDiagnosticAnswerRequest struct {
@@ -27,11 +28,19 @@ func (h Handler) createDiagnosticSession(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
+	lang := req.Lang
+	if lang == "" {
+		lang = r.Header.Get("X-Lang")
+	}
+	if lang == "" {
+		lang = "en"
+	}
 	session, err := h.diagnostic.CreateSession(r.Context(), interview.CreateSessionInput{
 		UserID:            req.UserID,
 		TargetRole:        req.TargetRole,
 		Stack:             req.Stack,
 		InterviewTimeline: req.InterviewTimeline,
+		Lang:              lang,
 	})
 	if err != nil {
 		writeError(w, http.StatusBadRequest, err.Error())