[Bug] The new proxy credentials have broken Icechunk commits

[eeholmes]

The new data.source.coop upload proxy supports PUT, GET, HEAD, DELETE,
If-Match, and If-None-Match, but returns 501 for S3 CopyObject:

NotImplemented: server-side copy (x-amz-copy-source) is not supported

Icechunk requires CopyObject during each commit to back up its small mutable
repo-info object before conditionally overwriting it. Writing icechunk stores to Source Coop now fails because of this.

Would it be possible to support same-bucket CopyObject, including
x-amz-copy-source-if-match? Even a GET+PUT fallback for small objects would
restore Icechunk compatibility.

Example code:

import boto3
import json
import uuid
from botocore.exceptions import ClientError

# I save the creds json from UI to this file
with open("source-creds.json") as f:
    creds = json.load(f)

s3 = boto3.client(
    "s3",
    endpoint_url=creds["endpoint_url"],
    region_name=creds["region_name"],
    aws_access_key_id=creds["aws_access_key_id"],
    aws_secret_access_key=creds["aws_secret_access_key"],
    aws_session_token=creds["aws_session_token"],
)

bucket = "fish-pace"
token = uuid.uuid4().hex
source_key = f"globcolour/copyobject-test/source-{token}.txt"
dest_key = f"globcolour/copyobject-test/dest-{token}.txt"

try:
    # Ordinary PUT succeeds
    put_response = s3.put_object(
        Bucket=bucket,
        Key=source_key,
        Body=b"copy test",
    )
    print("PUT:", put_response["ResponseMetadata"]["HTTPStatusCode"])

    source = s3.head_object(Bucket=bucket, Key=source_key)
    etag = source["ETag"]
    print("Source ETag:", etag)

    # Server-side CopyObject fails through data.source.coop
    copy_response = s3.copy_object(
        Bucket=bucket,
        Key=dest_key,
        CopySource={
            "Bucket": bucket,
            "Key": source_key,
        },
        CopySourceIfMatch=etag,
    )

    print(
        "COPY:",
        copy_response["ResponseMetadata"]["HTTPStatusCode"],
    )

except ClientError as e:
    print("HTTP status:", e.response["ResponseMetadata"]["HTTPStatusCode"])
    print("Error code:", e.response["Error"]["Code"])
    print("Message:", e.response["Error"]["Message"])

finally:
    for key in (source_key, dest_key):
        try:
            s3.delete_object(Bucket=bucket, Key=key)
        except Exception:
            pass

Gives this output

PUT: 200
Source ETag: "..."
HTTP status: 501
Error code: NotImplemented
Message: not implemented: server-side copy (x-amz-copy-source) is not supported

Icechunk uses CopyObject to back up its mutable repo object before each commit, so this causes Icechunk commits through https://data.source.coop to fail even though ordinary and conditional PutObject requests succeed.
https://github.com/earth-mover/icechunk/blob/d6e27c56af15edcb95c3cee616520e4a0d1f80ce/icechunk/src/asset_manager.rs#L1583-L1607

[alukach]

Thanks for the report. This had been reported in the Source Cooperative Slack, resulting in the following two issues created in multistore (the library underlying data.source.coop):

• Support S3 CopyObject (server-side copy via x-amz-copy-source) developmentseed/multistore#119
• Enforce conditional-write preconditions (If-Match / If-None-Match) on PutObject developmentseed/multistore#120

These fixes were released in https://github.com/developmentseed/multistore/releases/tag/v0.7.0 and are now live on https://data.staging.source.coop.

This PR will be closed by #192 (ie releasing to prod)

[alukach]

@eeholmes We've deployed #192 (and a subsequent #199) and I believe that these issues should now be resolved. I'm going to close this but please let me know if you continue to have issues (and we can re-open this issue)