Expected Behavior

When using Snowflake offline store, feature inference should consider VARCHAR columns in snowflake as str.

Current Behavior

When using Snowflake offline store, feature inference considers VARCHAR type columns in snowflake as object in pandas dataframe, and therefore cause UNKNOWN error.

https://github.com/feast-dev/feast/blob/master/sdk/python/feast/infra/offline_stores/snowflake_source.py#L196-L207

Steps to reproduce

Specifications

• Version: 0.18.0+
• Platform: mac os
• Subsystem:

Possible Solution

I would suggest changing ValueType.UNKNOWN to ValueType.STRING since pandas dtype object is str or mixed. And typically we just need it as string

https://github.com/feast-dev/feast/blob/master/sdk/python/feast/type_map.py#L532