kotlin parse jwt untrusted - ignore signature

jwtUntrusted.kt

// see: https://github.com/auth0-blog/spring-boot-jwts/blob/master/src/main/java/com/example/security/TokenAuthenticationService.java   

//Example: 
val json:String= JwtUntrusted.parseClaimsUntrustedToJson("Bearer xxx")

object JwtUntrusted {
        // requires (gradle): compile group: 'io.jsonwebtoken', name: 'jjwt', version: '0.9.0'
        private val JSON = jacksonObjectMapper()

        fun removeSignature(jwt:String) = jwt.replaceAfterLast(".", "").trim()
        fun removeBearer(jwt:String) = jwt.removePrefix("Bearer").trim()

        fun parseClaimsUntrusted(jwt: String) =
                jwt.let { removeSignature(it) }
                        .let { removeBearer(it) }
                        .let { Jwts.parser().parseClaimsJwt(it) }

        fun parseClaimsUntrustedToJson(jwt:String) =
                jwt.let { parseClaimsUntrusted(it) }
                        .let { JSON.writeValueAsString(it) }
        
        fun createToken(subject: String, expireIn:Duration): String {
            val expireAt=Instant.now() + expireIn
            val secret = "mysecret"
            return Jwts.builder()
                    .setSubject(subject)
                    .setClaims(mapOf(
                            "c1" to "C1",
                            "c2" to "C2"
                    ))
                    .setAudience("myaudience")
                    .setExpiration(Date.from(expireAt))
                    .signWith(SignatureAlgorithm.HS512, secret)
                    .compact()
        }
        
        fun createTokenFromPayload(payload: TokenPayload): String {
            val secret = "mysecret"
            return Jwts.builder()
                    .setPayload(JSON.writeValueAsString(payload))
                    .signWith(SignatureAlgorithm.HS512, secret)
                    .compact()
        }

        data class TokenPayload(
                val iss:String?=null,
                val sub:String?=null,
                val aud:List<String>?=null,
                val iat:Long?=null,
                val exp:Long?=null,
                val azp:String?=null,
                val scope:String?=null
        ) {
            companion object {
                fun of(
                        iss:String?=null,
                        sub:String?=null,
                        aud:List<String>?=null,
                        iat:Instant?=null,
                        exp:Instant?=null,
                        azp:String?=null,
                        scope:String?=null
                ) = TokenPayload(iss=iss, sub = sub, aud = aud, iat = iat?.epochSecond, exp = exp?.epochSecond, azp = azp, scope = scope)
            }
        }
    }