MessageImpl.setFinalContentType() mangles Content-Type

[patrick-peer]

com.sun.xml.messaging.saaj.soap.MessageImpl.setFinalContentType(String) uses com.sun.xml.messaging.saaj.packaging.mime.internet.ContentType.toString() to (re-)set the Content-Type. Quite ironically a comment there states that "SOAP message senders should send Content-Type headers on a single long line.", but the implementation of com.sun.xml.messaging.saaj.packaging.mime.internet.ParameterList.toString(int) introduces "\r\n\t" on overflows.

Example:
I want to deliberately set the string application/soap+xml;action="http://docs.oasis-open.org/ws-sx/ws-trust/200512/RST/Issue";charset=utf-8 as Content-Type, by calling com.synedra.xds.soap.messagebuilder.SoapMessageBuilder.setMimeHeader(String, String). What is actually sent over the wire is

Content-Type: application/soap+xml; charset=utf-8; \r\n
\taction="http://docs.oasis-open.org/ws-sx/ws-trust/200512/RST/Issue"\r\n

See also https://stackoverflow.com/questions/48413785/spring-integration-and-soap-1-2-setting-soapaction