fix clippy default warning

general: apply clippy lints (#407)

* general: update crates to 2021 edition.

* general: apply clippy --fix

* general: apply manual clippy lints

* cargo fmt.

Remove needless use of references
for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_mut_passed

Replace `assert!(false, …)`/`assert!(false)` with `panic!(…)`/`panic!()`

Unify `assert_eq!(…)`/`assert_ne!(…)` to take args in order of `…!(actual, expected)`

While there isn't an explicit convention for this in Rust the stdlib docs all use `assert_eq!(actual, expected)`

Unify `assert_eq!(…)`/`assert_ne!(…)` to take args in order of `…!(actual, expected)`

While there isn't an explicit convention for this in Rust the stdlib docs all use `assert_eq!(actual, expected)`, making it a sort of implicit convention.

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implement from and tryfrom string traits for SessionDescription (#348)

Extmap URI for video orientation

Move all to top level