Support for storing historical runs

Need to be able to manually specify creation, start and end times. To begin with:

• Run.init() needs additional options created, started and endtime (or similar). If not set, the server will set them (as it does now).
• Run.close() needs an additional timestamp option for specifying the end time. If not set, the server will set it (as it does now).

This doesn't take into account people using the context manager.

When creating a run the JSON body in the POST can include created and started. If there are no metrics then it can also include endtime and status set to completed. When updating the status of the run to completed the JSON body can include endtime.

首先跟踪 Run.init() 和 Run.close()，然后检查它们的 JSON body 是如何为创建和完成 run 组装的。考虑 context manager 路径，并验证可选的历史时间戳会保留当前服务器默认值，而已完成的 run 会发送必需的状态和结束时间。