Add submission validation and filtering to unauthenticated "pings" for outgoing link actions

As aspects of the timestamp updating (e.g. outgoing link "pings") are through non-authenticated submissions set up queueing/filtering in submission process to handle erroneous/malicious submissions.

Start by tracing the unauthenticated submission path for outgoing-link "pings" and identify where timestamp updates enter the queueing or filtering process. Define validation and filtering behavior for erroneous or malicious submissions, then verify that accepted and rejected submissions are handled as intended.

Written by the indexing model from the issue text.