Fix deployment

[ahuang11]

Closes PrefectHQ/prefect#7583 and #161

Apparently, cast_pathlib does not get called when you do self.storage.basepath so this makes type str and defaults to "" instead of None.

I was initially planning to submit a PR into Prefect to update: https://github.com/PrefectHQ/prefect/blob/main/src/prefect/deployments.py#L293-L309. However, I realized that since the concept of basepath in Prefect S3 is s3://--not the base path of the path and is never a pathlib.Path as in prefect-aws, I think it's more suitable for the PR to be here? Let me know if that makes sense.

Example

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[desertaxle]

This looks like it could be a breaking change. Can we verify if this still works if you provide a Path for basepath?

[ahuang11]

Hmm yeah you're right; I thought Pydantic would simply coerce into a string. Should I submit a PR to Prefect to fix then?

[desertaxle]

Would this work?

    basepath: Optional[Union[str, Path]] = Field(
        default="",
        description="Location to write to and read from in the S3 bucket. Defaults to "
        "the root of the bucket.",
    )

[ahuang11]

Okay that works!

from pathlib import Path
from prefect_aws import AwsCredentials
from prefect_aws.s3 import S3Bucket

aws_credentials = await AwsCredentials.load("my-credentials")
bucket = S3Bucket(bucket_name="andrew-int-test-cmd", aws_credentials=aws_credentials, basepath=Path("my/home/path"))
await bucket.save("test")

prefect deployment build ./log_flow.py:log_flow -n log-flow-s3 -sb s3-bucket/test