Feature request: Data sources without timestamps?

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I am researching how to integrate Feast with my model building process. We typically have some data sources that describe objects that have no timestamp. A canonical example is a geographical area. In theory they have changing characteristics, but for the problem scope for which we build a model, they are considered to be immutable, and our data contains no timestamp field for them. However, your documentation says [Feast uses a time-series data model to represent data](https://docs.feast.dev/v/master/getting-started/concepts/data-source)

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I would like a way to represent data sources which have no timestamp. Alternately, if this is already possible, I suggest making the documentation clearer on this issue.

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I could add dummy timestamps to data files.

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