feat!: revert `to_schema` overloads & optimize `upsert_many`

cofin commented 4 months ago

Description

This PR:

Reverts the previous to_schema implementation in the service layer. This will need to be rethought as it requires too many overloads to any customized service function.
Ensures that the filter values for upsert_many is a unique list. This is useful when you are merging a large amount of objects on a foreign key. The lookup will only contain a single unique entry for each key instead of one for each row.
Adds a schema_to_dict method to convert incoming Pydantic or Msgspec models to dictionaries
Adds additional type guard helpers to check for a field in a dictionary, Struct, or BaseModel