Break up Database impl into multiple files, organized by topic

crates/collab/src/db/queries.rs

@@ -0,0 +1,10 @@
+use super::*;
+
+pub mod access_tokens;
+pub mod channels;
+pub mod contacts;
+pub mod projects;
+pub mod rooms;
+pub mod servers;
+pub mod signups;
+pub mod users;