Object Store with IRSA not working

I have applied the following configuration to my cluster in order to enable WAL archiving.
My Object storage is S3, CNPG is running in EKS, and I want to configure access via IRSA.

Cluster:
```
apiVersion: postgresql.cnpg.io/v1
kind: Cluster
spec:
serviceAccountTemplate:
metadata:
annotations:
eks.amazonaws.com/role-arn: arn:aws:iam::
plugins:
- name: barman-cloud.cloudnative-pg.io
isWALArchiver: true
parameters:
barmanObjectName: objectstore
```

ObjectStore:
```
apiVersion: barmancloud.cnpg.io/v1
kind: ObjectStore
metadata:
name: objectstore
spec:
configuration:
data:
compression: bzip2
destinationPath: s3:///
wal:
compression: bzip2
maxParallel: 16
```

Policy attached to SA:
```
{
Action: [
"s3:PutObject",
"s3:GetObject",
"s3:ListBucket",
"s3:DeleteObject",
],
Effect: "Allow",
Resource: [
"arn:aws:s3:::",
"arn:aws:s3:::/*",
],
},
```

However, the WAL archiving is not working with the following error, complaining about missing Azure credentials even though my Object Storage is hosted by AWS.

```
{"level":"error","ts":"2025-08-13T17:06:02.383971021Z","logger":"wal-archive","msg":"Error while calling ArchiveWAL, failing","pluginName":"barman-cloud.cloudnative-pg.io","logging_pod":"metabase-database-3","error":"rpc error: code = Unknown desc = missing Azure credentials","stacktrace":"github.com/cloudnative-pg/machinery/pkg/log.(*logger).Error\n\tpkg/mod/github.com/cloudnative-pg/machinery@v0.3.0/pkg/log/log.go:125\ngithub.com/cloudnative-pg/cloudnative-pg/internal/cnpi/plugin/client.(*data).ArchiveWAL\n\tinternal/cnpi/plugin/client/wal.go:69\ngithub.com/cloudnative-pg/cloudnative-pg/pkg/management/postgres/archiver.archiveWALViaPlugins\n\tpkg/management/postgres/archiver/archiver.go:295\ngithub.com/cloudnative-pg/cloudnative-pg/pkg/management/postgres/archiver.internalRun\n\tpkg/management/postgres/archiver/archiver.go:156\ngithub.com/cloudnative-pg/cloudnative-pg/pkg/management/postgres/archiver.Run\n\tpkg/management/postgres/archiver/archiver.go:141\ngithub.com/cloudnative-pg/cloudnative-pg/internal/cmd/manager/walarchive.NewCmd.func1\n\tinternal/cmd/manager/walarchive/cmd.go:65\ngithub.com/spf13/cobra.(*Command).execute\n\tpkg/mod/github.com/spf13/cobra@v1.9.1/command.go:1015\ngithub.com/spf13/cobra.(*Command).ExecuteC\n\tpkg/mod/github.com/spf13/cobra@v1.9.1/command.go:1148\ngithub.com/spf13/cobra.(*Command).Execute\n\tpkg/mod/github.com/spf13/cobra@v1.9.1/command.go:1071\nmain.main\n\tcmd/manager/main.go:71\nruntime.main\n\t/opt/hostedtoolcache/go/1.24.5/x64/src/runtime/proc.go:283"}
```

Versions:
CNPG 1.26.1
Barman Cloud Plugin 0.5.0

Start by tracing the WAL archive path through internal/cnpi/plugin/client/wal.go and pkg/management/postgres/archiver/archiver.go, using the reported CNPG 1.26.1 and Barman Cloud Plugin 0.5.0 configuration as the reproduction context. Determine why this AWS S3 setup requests Azure credentials, then verify the behavior with an appropriate plugin or integration test; done means WAL archiving works through IRSA without the Azure-credential error.

Written by the indexing model from the issue text.