Prior to this commit, launching a GraphQL application without any schema
file or customizer bean would result in an exception caught by a
FailureAnalyzer telling the developer about configured locations.
Since then, a new client has been introduced in Spring GraphQL and the
mere presence of the GraphQL starter does not mean anymore that the
intent is to create a GraphQL API in the app: we could instead just
consume an existing, remote API.
This commit refines the GraphQL server auto-configuration so that it is
enabled only if:
* there is at least one schema file in the configured locations
* or a `GraphQlSourceCustomizer` bean has been defined in the app
These changes make the custom FailureAnalyzer useless and is also
removed as part of this commit.
Closes gh-30035
087e853c5d