feat：完善活动信息

app/api/enterprise/model/activity_join.go

@@ -0,0 +1,13 @@
+package model
+
+import (
+	"SciencesServer/app/common/model"
+)
+
+type ActivityJoin struct {
+	*model.ActivityJoin
+}
+
+func NewActivityJoin() *ActivityJoin {
+	return &ActivityJoin{model.NewActivityJoin()}
+}