[FEATURE] Support KEYS_ONLY secondary index

[flolas]

given a Example Table with secondary index that ha projection_type = 'KEYS_ONLY':

class Example(Dyntastic):
    __table_name__ = "example"
    __hash_key__ = "id"
    __table_host__ = "http://localhost:8000"
    __table_region__ = "us-east-1"

    some_required_attribute: str

when you get the results from dynamodb only return the __hash_key__ because of projection_type, this raises an error when calling the query() method because some_required_attribute is missing.

query_results = cls.query(
    A.is == id,
    index="example-index",
)

You can make optional all the fields to make this work, but I think that is a bad idea when using schema validation, lol.

Feature Idea: When querying secondary indexes with KEYS_ONLYS projection would be great to: (1) disable the validation of the pydantic schema upon getting the data and validate only keys and return the object with the partion keys only. (2) [optional argument for query] query method return the full object using GET operations after getting (1)

[nayaverdier]

Thanks for the feature request, definitely would like to support this for both query and scan. The tricky part will be running validation / parsing on the keys while ignoring all of the other fields. I'll try to get something out this week.

[nayaverdier]

@flolas This is supported in 0.12.0. You can pass load_full_item=True to automatically refresh and get the full item. I haven't tested with INCLUDE projection indexes, but it should also work in that case.