Calculate odds of association as additional data product

The joint FAR of RAVEN is not necessarily a good measure of whether two events are associated but rather whether a joint candidate is worth additional follow-up. Instead we could include the odds ratio of association as an additional data product to help RRT members make a decision regarding a joint candidate.

This could be calculated similar to https://arxiv.org/abs/2111.12814, using p-astro to get the GW Bayes factor B_n/s(gw)=P_ter/(1-P_ter). The rates used here would be somewhat speculative and would have fairly large error bars, so perhaps we would include both the upper and lower bounds as well.

This could be displayed on GraceDB similar to additional statistics provided by bayestar (Bayes factor of coherence, etc.)