Treat internal "seen" field as indicator for hijack True/False Pos ack

[vkotronis]

Is your feature request related to a problem? Please describe.
Right now we treat ignore as an implicit FP and resolve as an implicit TP.

Describe the solution you'd like
Use the already available field (orthogonal to the tagging mechanism), to help the user signal this explicitly. Ignore would still trigger a non-ack, while resolved and mitigate an ack.

Describe alternatives you've considered
New field, but since we already have an internal one (and we can do without migrating the DB again), this is quite cost-effective.

Additional context
N/A