Compilation error for dynamic keys

[XX]

When using keys as owned strings instead of &'static str:

slog = { version = "2.5.1", features = ["dynamic-keys"] }

this crate is not compiled:

Checking slog-kvfilter v0.7.0
error[E0277]: the trait bound `&str: std::borrow::Borrow<slog::Key>` is not satisfied
  --> /home/xx/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-kvfilter-0.7.0/src/lib.rs:38:69
   |
38 |         let matched = if let Some(keyvalues) = self.pending_matches.get(&key) {
   |                                                                     ^^^ the trait `std::borrow::Borrow<slog::Key>` is not implemented for `&str`

error[E0277]: the trait bound `slog::Key: std::cmp::Eq` is not satisfied
  --> /home/xx/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-kvfilter-0.7.0/src/lib.rs:38:69
   |
38 |         let matched = if let Some(keyvalues) = self.pending_matches.get(&key) {
   |                                                                     ^^^ the trait `std::cmp::Eq` is not implemented for `slog::Key`

error[E0277]: the trait bound `&'a str: std::borrow::Borrow<slog::Key>` is not satisfied
  --> /home/xx/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-kvfilter-0.7.0/src/lib.rs:48:34
   |
48 |             self.pending_matches.remove(&key);
   |                                  ^^^^^^ the trait `std::borrow::Borrow<slog::Key>` is not implemented for `&'a str`

error[E0277]: the trait bound `slog::Key: std::cmp::Eq` is not satisfied
  --> /home/xx/.cargo/registry/src/github.com-1ecc6299db9ec823/slog-kvfilter-0.7.0/src/lib.rs:48:34
   |
48 |             self.pending_matches.remove(&key);
   |                                  ^^^^^^ the trait `std::cmp::Eq` is not implemented for `slog::Key`

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0277`.
error: Could not compile `slog-kvfilter`.

[przygienda]

ok, help would be appreciated ;-)