[thekhegay]

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• The commit message follows our guidelines: https://github.com/nestjs/docs.nestjs.com/blob/master/CONTRIBUTING.md

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Docs
• Other... Please describe:

What is the current behavior?

Issue Number: N/A

Federation hint says subgraphs support subscriptions "with the subscriptions option" and for Mercurius gateway it is enough to set wsUrl for each service. Both are off for Mercurius. Its option is subscription (like on subscriptions page), subscriptions on MercuriusFederationDriver gives TS2561 "Did you mean to write 'subscription'?" and if forced past types WebSocket handshake gets 400. Gateway with only wsUrl also answers 400, it needs subscription: true itself

What is the new behavior?

Hint names both options (subscriptions for Apollo, subscription: true for Mercurius) and says Mercurius gateway needs subscription: true plus wsUrl for each service. Checked on @nestjs/mercurius 14.1.0 with mercurius 16.12.1 and @mercuriusjs/gateway 5.2.0, subscription goes through subgraph and through gateway with these settings

Does this PR introduce a breaking change?

• Yes
• No