Idea: Optimize simple boolean filters

I often have conditional filtering in my queries which causes beam to produce where clauses that look like `WHERE ((true) AND (true)) AND (true)...`. It seems it would be easy to clean this up when building the queries by just realizing that a known (`val_ True`) combined with `&&.` can simplify to one side or the other. I'm not sure if this is "in-scope" with this project, but if it were easy, it would make the resulting queries cleaner.

I could see an argument against this if one wanted to have a very clear 1-to-1 correspondence between the beam DSL and generated SQL.