fix(jans-auth-server): tx token replace failing with 500

[yuriyz]

Describe the bug

2024-05-31 14:24:14,635 ERROR [qtp1260134048-19] c4338390-9d37-4c62-88d5-aaa358f3d2f7 [as.server.token.ws.rs.TokenRestWebServiceImpl] (TokenRestWebServiceImpl.java:233) - A JS
ONObject text must begin with '{' at 1 [character 2 line 1]
org.json.JSONException: A JSONObject text must begin with '{' at 1 [character 2 line 1]
        at org.json.JSONTokener.syntaxError(JSONTokener.java:503) ~[json-20231013.jar:?]
        at org.json.JSONObject.<init>(JSONObject.java:208) ~[json-20231013.jar:?]
        at org.json.JSONObject.<init>(JSONObject.java:402) ~[json-20231013.jar:?]
        at io.jans.as.server.token.ws.rs.TxTokenService.fillPayload(TxTokenService.java:166) ~[classes/:?]
        at io.jans.as.server.token.ws.rs.TxTokenService.createTxTokenJwr(TxTokenService.java:281) ~[classes/:?]
        at io.jans.as.server.token.ws.rs.TxTokenService.createTxToken(TxTokenService.java:132) ~[classes/:?]
        at io.jans.as.server.token.ws.rs.TxTokenService.process(TxTokenService.java:106) ~[classes/:?]
        at io.jans.as.server.token.ws.rs.TxTokenService.processTxToken(TxTokenService.java:91) ~[classes/:?]
        at io.jans.as.server.token.ws.rs.TokenRestWebServiceImpl.requestAccessToken(TokenRestWebServiceImpl.java:224) ~[classes/:?]
        at io.jans.as.server.token.ws.rs.TokenRestWebServiceImpl$Proxy$_$$_WeldClientProxy.requestAccessToken(Unknown Source) ~[classes/:?]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?]
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
        at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[?:?]
        at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:1

POST /jans-auth/restv1/token HTTP/1.1
Content-Type: application/x-www-form-urlencoded

grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange&audience=http%3A%2F%2Ftrusted2.com&subject_token=eyJraWQiOiJjb25uZWN0XzViODA2OWM3LWM5MDQtNDM4Mi1iNDNkLWVlNWJmMzBhNjQwYV9zaWdfcnMyNTYiLCJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiJ9.eyJyY3R4Ijp7InJlcV9pcCI6IjY5LjE1MS43Mi4xMjMifSwiYXVkIjpbIjgzYmM2NWYyLWIxNTUtNGQxNS1iODBkLWFiMWY0ZDlhMjQwZCIsImh0dHA6Ly90cnVzdGVkLmNvbSJdLCJzdWIiOiIiLCJwdXJwIjoidHhuX3Rva2VuIiwiaXNzIjoiaHR0cHM6Ly9qZW5raW5zLWJ1aWxkLmphbnMuaW8iLCJhemQiOnsiY2xpZW50X2lkIjoiODNiYzY1ZjItYjE1NS00ZDE1LWI4MGQtYWIxZjRkOWEyNDBkIn0sInR4biI6ImZiNzg2OWY5LTE1ZjgtNDhjNS05OWE0LWI3ZjQzOGUxYjJjNCIsImV4cCI6MTcxNzE0NjE0NiwiaWF0IjoxNzE3MTQ1OTY2fQ.he89X74L_STMxA34FCA3Kms9t1VVeleemHIMZFmYOmvti75b0h13nNM6AafKhfp1mFL4sK6ZvxgfZlRwCSmQTe0TTS1y-zyOZbSlcFpynzNakCn2a0avItjlInuQ09fiRq4nHK3B4SjHA_DHY2xiJT3QAiuSO-dbyFBhCudf0mp2ZB2fADyYscLBtu8lD4kiMlm1puh9lbyUlUCFdGcGeRyvq_iXBS3YyRuDPVIm6eQxdEVrKEP6qJEY1tai7k5GvliLdogks3ZJ2CvB8yYzMaGvnipfjhyHtRoSIlrNhmNZhU3vZ2VBH2aS4fUzxSEGe7VJkgzKh6Honvdt5X1SBg&subject_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aaccess_token&requested_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Atxn-token&request_context=%7B%22req_ip%22%3A%2269.151.72.100%22%7D

-------------------------------------------------------
RESPONSE:
-------------------------------------------------------
HTTP/1.1 500
Cache-Control: no-store
Connection: close
Content-Length: 0

[yuriyz]