Customize SimpleDataFetcherExceptionHandler to avoid logException for certain errors

[williamwjs]

Is your feature request related to a problem? Please describe.
In our app, it is normal and expected to have non-login users accessing the pages, where we will return as auth error for some queries. It is annoying to always log the stacktrace for such cases.

Graphql-Java made that a protected method so that we could override it with our own logic:
https://github.com/graphql-java/graphql-java/blob/master/src/main/java/graphql/execution/SimpleDataFetcherExceptionHandler.java#L40-L48

However, it is not easy to embed it with kickstart library right now.

Describe the solution you'd like
Expecting a non-required bean for DataFetcherExceptionHandler, so that it could be passed into the below places when building Execution strategy:

graphql-spring-boot/graphql-spring-boot-autoconfigure/src/main/java/graphql/kickstart/spring/web/boot/GraphQLWebAutoConfiguration.java

Lines 177 to 178 in 13cd484

	return new DefaultExecutionStrategyProvider(new AsyncExecutionStrategy(), null,
	new SubscriptionExecutionStrategy());

Describe alternatives you've considered
As a workaround, I have to provide my own bean for executionStrategies, which I feel is too much layer above:

graphql-spring-boot/graphql-spring-boot-autoconfigure/src/main/java/graphql/kickstart/spring/web/boot/GraphQLWebAutoConfiguration.java

Line 113 in 13cd484

private Map<String, ExecutionStrategy> executionStrategies;

[williamwjs]

A related question: May I also ask why line 177 gives null for mutationExecutionStrategy?

graphql-spring-boot/graphql-spring-boot-autoconfigure/src/main/java/graphql/kickstart/spring/web/boot/GraphQLWebAutoConfiguration.java

Lines 177 to 178 in 13cd484

	return new DefaultExecutionStrategyProvider(new AsyncExecutionStrategy(), null,
	new SubscriptionExecutionStrategy());