Fix GraphQL Explorer

[MikeAlhayek]

Fix #15304

@lampersky can you please checkout this branch and confirm that it fixes your issues?

The exception states

System.InvalidOperationException: 'This graph type 'AliasInputObjectType' with name 'AliasPartInput' has already been initialized. Make sure that you do not use the same instance of a graph type in multiple schemas. It may be so if you registered this graph type as singleton; see https://graphql-dotnet.github.io/docs/getting-started/dependency-injection/ for more info.'

[MikeAlhayek]

@hyzx86 can you please review the changes in this PR?

[sebastienros]

I did this change I believe (not even sure but seems familiar). And the comments states it is singleton, so the comment could be removed "if this is the correct thing to do". Have you tried to understand what the issue was with the resolution? It really can't be a singleton?

[MikeAlhayek]

@sebastienros I updated the description in the PR to show the detailed in the exception. I am guessing after the upgrade, we no longer need it to be singleton. And after the change everything seems to be working as expected. These types are resolved once during the schema building.

[sebastienros]

Tried on my side and came to the same solution, using Transient though. Each type shouldn't be resolved multiple time during a request that builds the schema.

[lampersky]

@MikeAlhayek, @sebastienros I've just tried ma/fix-graphql branch, and can't repro the issue anymore, so it looks the fix is solving the issue. Scheme is reloaded properly and GraphiQL explorer works as expected.

I only can see plenty of exceptions, when navigating from Admin/GraphQL to /Admin/Contents/ContentItems, but this is not related to issue reported earlier:

[gvkries]

Note that by making the graph types Scoped, it is not possible to resolve them automatically while building the schema. That means using something like

Field<[GraphType]>("Foo")
  .Description("bar")
  .ResolveAsync(x =>
  {
    [...]
  });

fails for complex types, because the ISchemaFactory is a singleton and a scoped [GraphType] cannot be resolved. This happens when a graph type depends on another one.
Also note that any scoped instance may still be referenced by the schema.

[hyzx86]

@hyzx86 can you please review the changes in this PR?

Sorry, I didn't notice this PR. When I saw it in the message list, it was already merged and I turned it off.