feat: execute graphQLRequest out of reactor netty threads ( cherry pick #1943) (#1945)

### 📝 Description
as soon as request was deserialized, move execution of operation out of
the thread that routed the request (reactor netty http epoll thread in
case of spring).

Author: samuelAndalon

servers/graphql-kotlin-server/src/main/kotlin/com/expediagroup/graphql/server/execution/GraphQLServer.kt

@@ -19,8 +19,10 @@ package com.expediagroup.graphql.server.execution
 import com.expediagroup.graphql.server.types.GraphQLResponse
 import com.expediagroup.graphql.server.types.GraphQLServerResponse
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.withContext
 import kotlin.coroutines.CoroutineContext
 import kotlin.coroutines.EmptyCoroutineContext
 
@@ -46,19 +48,21 @@ open class GraphQLServer<Request>(
     ): GraphQLServerResponse? =
         coroutineScope {
             requestParser.parseRequest(request)?.let { graphQLRequest ->
-                val deprecatedContext = contextFactory.generateContext(request)
-                val contextMap = contextFactory.generateContextMap(request)
+                withContext(Dispatchers.Default) {
+                    val deprecatedContext = contextFactory.generateContext(request)
+                    val contextMap = contextFactory.generateContextMap(request)
 
-                val customCoroutineContext = (deprecatedContext?.graphQLCoroutineContext() ?: EmptyCoroutineContext) +
-                    (contextMap[CoroutineContext::class] as? CoroutineContext ?: EmptyCoroutineContext)
-                val graphQLExecutionScope = CoroutineScope(
-                    coroutineContext + customCoroutineContext + SupervisorJob()
-                )
-                val graphQLContext = contextMap + mapOf(
-                    CoroutineScope::class to graphQLExecutionScope
-                )
+                    val customCoroutineContext = (deprecatedContext?.graphQLCoroutineContext() ?: EmptyCoroutineContext) +
+                        (contextMap[CoroutineContext::class] as? CoroutineContext ?: EmptyCoroutineContext)
+                    val graphQLExecutionScope = CoroutineScope(
+                        coroutineContext + customCoroutineContext + SupervisorJob()
+                    )
+                    val graphQLContext = contextMap + mapOf(
+                        CoroutineScope::class to graphQLExecutionScope
+                    )
 
-                requestHandler.executeRequest(graphQLRequest, deprecatedContext, graphQLContext)
+                    requestHandler.executeRequest(graphQLRequest, deprecatedContext, graphQLContext)
+                }
             }
         }
 }