[BUG] java-feign client try to decode xml reponse as json

generated Api code is like

  @RequestLine("GET /report/detail?testNo={testNo}&type={type}")
  @Headers({
    "Accept: application/xml",
  })
  ReportDetailRes getReportDetail(@Param("testNo") String testNo, @Param("type") String type);

when calling api, it reports:

Caused by: com.fasterxml.jackson.core.JsonParseException: Unexpected character ('<' (code 60)): expected a valid value (number, String, array, object, 'true', 'false' or 'null')
 at [Source: (BufferedReader); line: 1, column: 2]
	at com.fasterxml.jackson.core.JsonParser._constructError(JsonParser.java:1804) ~[jackson-core-2.9.9.jar:2.9.9]
	at com.fasterxml.jackson.core.base.ParserMinimalBase._reportError(ParserMinimalBase.java:693) ~[jackson-core-2.9.9.jar:2.9.9]
	at com.fasterxml.jackson.core.base.ParserMinimalBase._reportUnexpectedChar(ParserMinimalBase.java:591) ~[jackson-core-2.9.9.jar:2.9.9]
	at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._handleOddValue(ReaderBasedJsonParser.java:1902) ~[jackson-core-2.9.9.jar:2.9.9]
	at com.fasterxml.jackson.core.json.ReaderBasedJsonParser.nextToken(ReaderBasedJsonParser.java:757) ~[jackson-core-2.9.9.jar:2.9.9]
	at com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:4141) ~[jackson-databind-2.9.9.jar:2.9.9]
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4000) ~[jackson-databind-2.9.9.jar:2.9.9]
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3063) ~[jackson-databind-2.9.9.jar:2.9.9]
	at feign.jackson.JacksonDecoder.decode(JacksonDecoder.java:61) ~[feign-jackson-10.11.jar:?]
	at feign.AsyncResponseHandler.decode(AsyncResponseHandler.java:115) ~[feign-core-10.11.jar:?]
	at feign.AsyncResponseHandler.handleResponse(AsyncResponseHandler.java:87) ~[feign-core-10.11.jar:?]

Start with the generated Api code and trace the response path through feign.jackson.JacksonDecoder and feign.AsyncResponseHandler. Determine how application/xml responses are selected for decoding, then add regression coverage showing that the generated client no longer sends XML responses through the JSON decoder.