Enable to set dgs.graphql.websocket.path in webflux

[jvalde]

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• [ ] Consider creating a discussion on the discussion forum first
• [x] Make sure the PR doesn't introduce backward compatibility issues
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Pull Request type

• [ ] Bugfix
• [x] Feature
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] Other (please describe):

Changes in this PR

Allow to configure dgs.graphql.websocket.path in webflux so /subscriptions can be changed