Define an OpenAPI Security Scheme.
This macro will generate 1 implementation, [`SecurityScheme`].
## Example
```rust
use predawn::SecurityScheme;
/// This doc will be used as the tag description
#[derive(SecurityScheme)]
#[api_key(in = header, name = "X-API-Key")]
pub struct ApiKeyScheme;
#[derive(SecurityScheme)]
#[http(scheme = basic, rename = "Basic Auth")]
pub struct HttpScheme;
```
`rename` is optional, default is the type name.
[`SecurityScheme`]: https://docs.rs/predawn/latest/predawn/trait.SecurityScheme.html