refactor(lib): resolve unused import

[Ticsmtc]

running default build command

cargo build

reports

warning: unused import: `http::header::HeaderName`
 --> src/ext.rs:4:5
  |
4 | use http::header::HeaderName;
  |     ^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

[Ticsmtc]

cargo build --release 

reports

warning: variant is never constructed: `Internal`
  --> src/error.rs:78:5
   |
78 |     Internal,
   |     ^^^^^^^^
   |
   = note: `#[warn(dead_code)]` on by default

[seanmonstar]

Thanks :D