fix : enable to set dgs.graphql.graphiql.path in webflux

[heoYH]

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Pull Request type

• Bugfix
• Feature
• Refactoring (no functional changes, no api changes)
• Build related changes
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Changes in this PR

dgs.graphql.graphiql.path(https://netflix.github.io/dgs/configuration/) configuration does not work in webflux

Alternatives considered

• add graphiql path property in DgsWebfluxConfigurationProperties
• change the redirect path to 'dgs.graphql.graphiql.path' + /index.html
• 'dgs.graphql.graphiql.path'+/index.html path request is return the "classpath:/static/graphiql/index.html" resource
• add custom path test case

[berngp]

Thanks for the PR @heoYH .