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Support for the “extensions” field in GraphQL Request JSON Payloads

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For Query and Mutation

Cosmo Router supports sending the “extensions” field to Subgraphs. If a client sends an “extensions” field alongside a Query or Mutation, or alternatively as part of the “payload” of a Subscription Request, Cosmo Router will by default include the “extensions” field in all Subgraph requests. This feature allows you to extend GraphQL in a very flexible way as defined by the GraphQL over HTTP specification. Here’s an example on how this can be used: 
{"query":"{hello}","extensions":{"token":"asd"}}

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For initiating a subscription

Alternatively, this feature could be useful to send a token when initiating a subscription: 
{"id":"1","type":"subscribe","payload":{"extensions":{"token":"asd"},"query":"subscription {\n  currentTime {\n    unixTime\n  }\n}"}}
More info on how this can be used with subscriptions can be found here.