[visits] Set-up specific Scanning Visits

[skarya22]

• CCNA would like to set-up scanning visits, similar to how sites have a scanning designation- other projects would likely benefit from this as well
• On CCNA we have it set where scanning visits can only take place at scanning sites, and scanning sites can only have scanning visits. This is to be discussed on whether this behaviour is desired for all projects
• The current thought process is to add a column to the visit table similar to psc, which designates the visit as a scanning visit

[ridz1208]

1. I don't think Sites have any "scanning designation" (AFAIK)
2. I like the Idea
3. it would be my feeling too but in the context of LORIS I think PSC needs a similar column too