Fix loading of blocks

[ahuang11]

Summary

With the latest release of v0.2.1, defining target configs in code and get_configs worked.

from prefect import flow
from prefect_dbt.cli.configs import SnowflakeTargetConfigs
from prefect_snowflake.credentials import SnowflakeCredentials
from prefect_snowflake.database import SnowflakeConnector

@flow()
def test_flow():
    credentials = SnowflakeCredentials(
        user="user",
        password="password",
        account="account.region.aws",
        role="role",
    )
    connector = SnowflakeConnector(
        schema="public",
        database="database",
        warehouse="warehouse",
        credentials=credentials,
    )
    target_configs = SnowflakeTargetConfigs(
        connector=connector
    )
    return target_configs.get_configs()

print(test_flow())

However, when loading:

>>> from prefect_dbt.cli.configs import SnowflakeTargetConfigs
>>>
>>> snowflake_target_configs = SnowflakeTargetConfigs.load("my-snowflake")

Outputs:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/andrew/Applications/python/prefect/src/prefect/utilities/asyncutils.py", line 212, in wrapper
    return run_async_in_new_loop(async_fn, *args, **kwargs)
  File "/Users/andrew/Applications/python/prefect/src/prefect/utilities/asyncutils.py", line 141, in run_async_in_new_loop
    return anyio.run(partial(__fn, *args, **kwargs))
  File "/Users/andrew/mambaforge/envs/prefect-dbt/lib/python3.10/site-packages/anyio/_core/_eventloop.py", line 70, in run
    return asynclib.run(func, *args, **backend_options)
  File "/Users/andrew/mambaforge/envs/prefect-dbt/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 292, in run
    return native_run(wrapper(), debug=debug)
  File "/Users/andrew/mambaforge/envs/prefect-dbt/lib/python3.10/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/Users/andrew/mambaforge/envs/prefect-dbt/lib/python3.10/asyncio/base_events.py", line 646, in run_until_complete
    return future.result()
  File "/Users/andrew/mambaforge/envs/prefect-dbt/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 287, in wrapper
    return await func(*args)
  File "/Users/andrew/Applications/python/prefect/src/prefect/blocks/core.py", line 652, in load
    return cls._from_block_document(block_document)
  File "/Users/andrew/Applications/python/prefect/src/prefect/blocks/core.py", line 554, in _from_block_document
    block._block_document_id = block_document.id
  File "pydantic/main.py", line 358, in pydantic.main.BaseModel.__setattr__
ValueError: "SnowflakeTargetConfigs" object has no field "_block_document_id"

Apparently, cannot forbid extra fields.

Relevant Issue(s)

Checklist

• Summarized PR's changes in CHANGELOG.md