Use of state parameter in authorisation code flow

It seems like the state parameter is supported in the implementation, but not sure how it is used in the AS side. Could you give an example when granting code, how the server can callback also the state value?

Start by reviewing the authorization-code flow in the authorization-server implementation and trace how the state parameter is handled when granting a code. Document an example showing how the server returns the state value in its callback; the issue does not name a file or test to run.

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