add proc macro derive for `ApiError`

[mellowagain]

fixes FP-3863

usage:

#[derive(Debug, Error, Serialize, Deserialize, ApiError)]
#[serde(tag = "error", content = "details", rename_all = "camelCase")]
pub enum CommonError {
    #[api_error(status_code = StatusCode::INTERNAL_SERVER_ERROR)]
    #[error("Internal server error")]
    InternalServerError,
}