fix: fixes error handling for unsigned streaming upload malformed encoding

Fixes #1666
Fixes #1660

Unsigned streaming payload trailers have strict encoding rules for the request body. If the body isn’t encoded correctly, the expected `IncompleteBody` API error is now returned. Incorrect encoding includes things like invalid chunk sizes, missing delimiters, or malformed `\r\n` sequences.

s3err/s3err.go

@@ -88,6 +88,7 @@ const (
 	ErrInvalidCompleteMpPartNumber
 	ErrInternalError
 	ErrNonEmptyRequestBody
+	ErrIncompleteBody
 	ErrInvalidCopyDest
 	ErrInvalidCopySourceRange
 	ErrInvalidCopySourceBucket
@@ -328,6 +329,11 @@ var errorCodeResponse = map[ErrorCode]APIError{
 		Description:    "The request included a body. Requests of this type must not include a non-empty body.",
 		HTTPStatusCode: http.StatusBadRequest,
 	},
+	ErrIncompleteBody: {
+		Code:           "IncompleteBody",
+		Description:    "The request body terminated unexpectedly",
+		HTTPStatusCode: http.StatusBadRequest,
+	},
 	ErrInvalidPart: {
 		Code:           "InvalidPart",
 		Description:    "One or more of the specified parts could not be found.  The part may not have been uploaded, or the specified entity tag may not match the part's entity tag.",