Return a mutable {@code MessageHeaderAccessor} for the given message attempting
to match the type of accessor used to create the message headers, or otherwise
wrapping the message with a {@code MessageHeaderAccessor} instance.
<p>This is for cases where a header needs to be updated in generic code
while preserving the accessor type for downstream processing.
@return an accessor of the required type (never {@code null})
@since 4.1
Return a mutable {@code MessageHeaderAccessor} for the given message attempting to match the type of accessor used to create the message headers, or otherwise wrapping the message with a {@code MessageHeaderAccessor} instance. <p>This is for cases where a header needs to be updated in generic code while preserving the accessor type for downstream processing. @return an accessor of the required type (never {@code null}) @since 4.1