[FEATURE] Enable users providing field-level description and carry it over to JSON schema

[georgeh0]

Since #795 is resolved, we can enable users providing field-level description and carry it over to JSON schema!

We want to add a description field to FieldSchema:

• Rust type. Should be in Arc<str> type.
• Python type
• Create FieldSchema based on pydantic model: code
• Then we can put that into the Json schema: Json schema builder code

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[belloibrahv]

I'm ready to take on this issue to enable field-level descriptions. Please assign it to me.