error: direct implementation of `ToString`
  --> src/query_builder/update.rs:20:1
   |
20 | / impl ToString for UpdateAssignment {
21 | |     fn to_string(&self) -> String {
22 | |         match self {
23 | |             UpdateAssignment::Simple(name) => format!("{name} = ?"),
...  |
27 | |     }
28 | | }
   | |_^
   |
   = help: prefer implementing `Display` instead
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#to_string_trait_impl
   = note: `-D clippy::to-string-trait-impl` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::to_string_trait_impl)]`