throw & catch new InvalidPayloadException to return Unsupported Media Type for invalid POST payload

Author: TheDome0

servers/graphql-kotlin-ktor-server/src/main/kotlin/com/expediagroup/graphql/server/ktor/GraphQLStatusPages.kt

@@ -31,6 +31,7 @@ fun StatusPagesConfig.defaultGraphQLStatusPages(): StatusPagesConfig {
     exception<Throwable> { call, cause ->
         when (cause) {
             is UnsupportedOperationException -> call.respond(HttpStatusCode.MethodNotAllowed)
+            is InvalidPayloadException -> call.respond(HttpStatusCode.UnsupportedMediaType)
             else -> call.respond(HttpStatusCode.BadRequest)
         }
     }

servers/graphql-kotlin-ktor-server/src/main/kotlin/com/expediagroup/graphql/server/ktor/KtorGraphQLRequestParser.kt

@@ -31,6 +31,8 @@ internal const val REQUEST_PARAM_QUERY = "query"
 internal const val REQUEST_PARAM_OPERATION_NAME = "operationName"
 internal const val REQUEST_PARAM_VARIABLES = "variables"
 
+class InvalidPayloadException(message: String, throwable: Throwable) : IllegalStateException(message, throwable)
+
 /**
  * GraphQL Ktor [ApplicationRequest] parser.
  */
@@ -62,6 +64,6 @@ open class KtorGraphQLRequestParser(
     private suspend fun parsePostRequest(request: ApplicationRequest): GraphQLServerRequest? = try {
         request.call.receive()
     } catch (e: IOException) {
-        throw IllegalStateException("Invalid HTTP request - unable to parse GraphQL request from POST payload", e)
+        throw InvalidPayloadException("Invalid HTTP request - unable to parse GraphQL request from POST payload", e)
     }
 }