Added new episode to relay docs

website/src/docs/hotchocolate/defining-a-schema/relay.md

@@ -12,6 +12,10 @@ As part of a specification Relay proposes some schema design principles for Grap
 
 [Learn more about the Relay GraphQL Server Specification](https://relay.dev/docs/guides/graphql-server-specification)
 
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 # Global identifiers
 
 If an output type contains an `id: ID!` field, [Relay](https://relay.dev) and other GraphQL clients will consider this the unique identifier of the entity and might use it to construct a flat cache. This can be problematic, since we could have the same identifier for two of our types. When using a database for example, a `Foo` and `Bar` entity could both contain a row with the identifier `1` in their respective tables.