Write user code example

```[tasklist]
### Tasks
- [x] User code for the continual summarization task (Scenario 2)
- [ ] Make it clearer what are the learning settings, including learning_constraints, learning_objectives, learning_results, and learning_data in the continual summarization task.
- [ ] User code for Scenario 1: Use historical interaction log to improve an agent's performance with the accumulation of interaction sessions.
- [ ] To discuss is "learning" the precise word to use. Other alternatives include "digesting", "observing"?
- [ ] Questions to discuss: what are the objectives? For example, "improving user experience" could be a high-level objective. But what are good quantitative measures for it? What is a good measurement of "improvement". Potential metrics include: the number of turns to finish a task, the cost for finising a task.
```