Subscriptions: make validation errors non-terminal

Author: martinbonnin

apollo-execution-runtime/src/commonMain/kotlin/com/apollographql/execution/ExecutableSchema.kt

@@ -44,7 +44,7 @@ class ExecutableSchema(
   ): Flow<SubscriptionEvent> {
     return prepareRequest(schema, coercings, persistedDocumentCache, request).fold(
       ifLeft = {
-        flowOf(SubscriptionError(it))
+        flowOf(SubscriptionResponse(GraphQLResponse.Builder().errors(it).build()))
       },
       ifRight = {
         operationContext(it, executionContext).subscribe()

apollo-execution-runtime/src/commonMain/kotlin/com/apollographql/execution/SubscriptionEvent.kt

@@ -18,5 +18,7 @@ class SubscriptionResponse(val response: GraphQLResponse) : SubscriptionEvent
  * This event is terminal and the client can decide whether to retry or give up.
  * For convenience, [SubscriptionError] uses the same error type as the GraphQL errors but these are not in the same domain. Another server
  * implementation could decide to use something else.
+ *
+ * Example: validation error
  */
 class SubscriptionError(val errors: List<Error>) : SubscriptionEvent