GetExchangeRequest has a required party field.

[SanjayVas]

GetExchangeRequest currently has a required oneof field named party.

From AIP-131:

The request message must not contain any other required fields, and should not contain other optional fields except those described in another AIP.

The implementation checks whether the authenticated user matches this field, and furthermore uses the value in the underlying query. Instead, the implementation should read the Exchange and then check whether it matches the caller.

[SanjayVas]

Fixed by #137 and world-federation-of-advertisers/cross-media-measurement#1028