Now it's much clearer when looking at the code, that these routes are about
project-hosted tickets, and it's easier to see where the author-hosted
equivalents are missing.
- WorkflowField now has a color, it's a simple `Maybe Int` for now. Valid
values are only 1-4
- That color is used for displaying ticket class params a.k.a labels in ticket
list view
- Ticket list now also serves a paged OrderedCollection
I tried to use a single SQL query to grab the tickets along with their labels,
but couldn't figure out a way to aggregate tuples/rows into an array (it seems
only single values are supported in Esqueleto). Instead of doing manual SQL or
adding Esqueleto functions, I just switched from 1 query to O(n) queries: Each
ticket has its own query selecting its labels. I guess it's slower, but also,
ticket list is paged now with fixed page size so it's really O(1) ^_^
