open class KtorGraphQLRequestParser (#1856)

Added open modifier for class KtorGraphQLRequestParser to support custom
logic for request parser

Author: JajaComp

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

@@ -34,7 +34,7 @@ internal const val REQUEST_PARAM_VARIABLES = "variables"
 /**
  * GraphQL Ktor [ApplicationRequest] parser.
  */
-class KtorGraphQLRequestParser(
+open class KtorGraphQLRequestParser(
     private val mapper: ObjectMapper
 ) : GraphQLRequestParser<ApplicationRequest> {