deps: update vendor dependencies for S3-compatible storage

Updates AWS SDK and removes Blazer B2 dependency in favor of unified
S3-compatible approach. Includes configuration examples and documentation.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

vendor/github.com/aws/aws-sdk-go/service/s3/customizations.go

@@ -0,0 +1,89 @@
+package s3
+
+import (
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/client"
+	"github.com/aws/aws-sdk-go/aws/endpoints"
+	"github.com/aws/aws-sdk-go/aws/request"
+	"github.com/aws/aws-sdk-go/internal/s3shared/arn"
+	"github.com/aws/aws-sdk-go/internal/s3shared/s3err"
+)
+
+func init() {
+	initClient = defaultInitClientFn
+	initRequest = defaultInitRequestFn
+}
+
+func defaultInitClientFn(c *client.Client) {
+	if c.Config.UseDualStackEndpoint == endpoints.DualStackEndpointStateUnset {
+		if aws.BoolValue(c.Config.UseDualStack) {
+			c.Config.UseDualStackEndpoint = endpoints.DualStackEndpointStateEnabled
+		} else {
+			c.Config.UseDualStackEndpoint = endpoints.DualStackEndpointStateDisabled
+		}
+	}
+
+	// Support building custom endpoints based on config
+	c.Handlers.Build.PushFront(endpointHandler)
+
+	// Require SSL when using SSE keys
+	c.Handlers.Validate.PushBack(validateSSERequiresSSL)
+	c.Handlers.Build.PushBack(computeSSEKeyMD5)
+	c.Handlers.Build.PushBack(computeCopySourceSSEKeyMD5)
+
+	// S3 uses custom error unmarshaling logic
+	c.Handlers.UnmarshalError.Clear()
+	c.Handlers.UnmarshalError.PushBack(unmarshalError)
+	c.Handlers.UnmarshalError.PushBackNamed(s3err.RequestFailureWrapperHandler())
+}
+
+func defaultInitRequestFn(r *request.Request) {
+	// Add request handlers for specific platforms.
+	// e.g. 100-continue support for PUT requests using Go 1.6
+	platformRequestHandlers(r)
+
+	switch r.Operation.Name {
+	case opGetBucketLocation:
+		// GetBucketLocation has custom parsing logic
+		r.Handlers.Unmarshal.PushFront(buildGetBucketLocation)
+	case opCreateBucket:
+		// Auto-populate LocationConstraint with current region
+		r.Handlers.Validate.PushFront(populateLocationConstraint)
+	case opCopyObject, opUploadPartCopy, opCompleteMultipartUpload:
+		r.Handlers.Unmarshal.PushFront(copyMultipartStatusOKUnmarshalError)
+		r.Handlers.Unmarshal.PushBackNamed(s3err.RequestFailureWrapperHandler())
+	case opPutObject, opUploadPart:
+		r.Handlers.Build.PushBack(computeBodyHashes)
+		// Disabled until #1837 root issue is resolved.
+		//	case opGetObject:
+		//		r.Handlers.Build.PushBack(askForTxEncodingAppendMD5)
+		//		r.Handlers.Unmarshal.PushBack(useMD5ValidationReader)
+	case opWriteGetObjectResponse:
+		r.Handlers.Build.PushFront(buildWriteGetObjectResponseEndpoint)
+	}
+}
+
+// bucketGetter is an accessor interface to grab the "Bucket" field from
+// an S3 type.
+type bucketGetter interface {
+	getBucket() string
+}
+
+// sseCustomerKeyGetter is an accessor interface to grab the "SSECustomerKey"
+// field from an S3 type.
+type sseCustomerKeyGetter interface {
+	getSSECustomerKey() string
+}
+
+// copySourceSSECustomerKeyGetter is an accessor interface to grab the
+// "CopySourceSSECustomerKey" field from an S3 type.
+type copySourceSSECustomerKeyGetter interface {
+	getCopySourceSSECustomerKey() string
+}
+
+// endpointARNGetter is an accessor interface to grab the
+// the field corresponding to an endpoint ARN input.
+type endpointARNGetter interface {
+	getEndpointARN() (arn.Resource, error)
+	hasEndpointARN() bool
+}