Support observing changes to single properties

Note these related feature requests:

• #126
• #268

Translation:
I hope to support custom models to query. For example, the storage model is A. I want to use B to accept only some fields of the same name of A to ensure memory overhead. For example, when I do tabular data, I want to query some fields of model A (due to model A There are more than 20 fields) I only want to monitor some of the fields in this model. The current monitoring is full, which will result in a complete model of 20,000 data observations and 200,000 data. For example, I only want to monitor changes and get this Twenty thousand ids, then 20,000 complete model objects will not be generated. This function room provides

Original issue:
希望支持自定义模型来查询 比如存储模型是A 我希望用B 来接受 B只有A的一些同名字段 来保证内存开销

希望支持自定义模型来查询 比如存储模型是A 我希望用B 来接受 B只有A的一些同名字段 来保证内存开销
比如我在做表格数据的时候 希望查询出模型A的部分字段(由于模型A的字段已经超过20个) 我只想监听 这个模型中的部分字段
目前的监听 是全量的 会导致有2万条数据 观察返回也返回了20万条数据的完整模型 比如我只想监听改变而得到这两万个id,那么不会产生2万个完整的模型对象 这个功能room有提供

Start by reviewing related feature requests #126 and #268 and the translated description, since no source file or test is named. Clarify how observing selected properties should work and verify that completion means receiving changes or IDs without creating full model objects for every observed record.