Improve config options for missing and dropping db columns.

Implement actual drop functionality.

Signed-off-by: Jason Volk <jason@zemos.net>

src/database/Cargo.toml

@@ -57,6 +57,7 @@ async-channel.workspace = true
 const-str.workspace = true
 ctor.workspace = true
 futures.workspace = true
+itertools.workspace = true
 log.workspace = true
 minicbor.workspace = true
 minicbor-serde.workspace = true