Hey, I'm using

aws.directconnect.GatewayAssociationProposal

to initiate a cross-account connection to a direct connect gateway. The problem I have though is that once I have accepted the proposal, Pulumi still tries to delete this resource when destroying the stack...

aws:directconnect:GatewayAssociationProposal (assocToMainDcGateway):
    error: deleting urn:pulumi:web-testing::web-platform-vpc::aws:directconnect/gatewayAssociationProposal:GatewayAssociationProposal::assocToMainDcGateway: 1 error occurred:
        * error deleting Direct Connect Gateway Association Proposal (49017cb1-925c-4ffb-aef2-4cdf0a853795): DirectConnectClientException: Direct Connect Gateway Association Proposal 49017cb1-925c-4ffb-aef2-4cdf0a853795 is not found

Is there a way to create a resource in Pulumi, but not register it to the Pulumi state?

You can remove the resource from the state using the CLI: https://www.pulumi.com/docs/reference/cli/pulumi_state_delete/