Follow up to: https://github.com/hashicorp/consul/pull/10738#discussion_r680190210
Previously we were passing an Authorizer that would always allow the
operation, then later checking the authorization using vetServiceTxnOp.
On the surface this seemed strange, but I think it was actually masking
a bug as well. Over time `servicePreApply` was changed to add additional
authorization for `service.Proxy.DestinationServiceName`, but because
we were passing a nil Authorizer, that authorization was not handled on
the txn_endpoint.
`TxnServiceOp.FillAuthzContext` has some special handling in enterprise,
so we need to make sure to continue to use that from the Txn endpoint.
This commit removes the `vetServiceTxnOp` function, and passes in the
`FillAuthzContext` function so that `servicePreApply` can be used by
both the catalog and txn endpoints. This should be much less error prone
and prevent bugs like this in the future.
c718de730b