Implement std::error::Error for our custom errors

For allowing a more ergonomic use and better integration on the
ecosystem, this adds the `std::error::Error` `impl` for our custom
errors.

We intent to drop this hand made code once `derive_more` finishes the
addition of the Error derive support[1]. Until that is available, we
need to live with that.

1. https://github.com/JelteF/derive_more/issues/92

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>

src/error.rs

@@ -21,6 +21,8 @@ pub enum UrlGenerationError {
     ParseError(UrlParseError),
 }
 
+impl std::error::Error for UrlGenerationError {}
+
 /// `InternalServerError` for `UrlGeneratorError`
 impl ResponseError for UrlGenerationError {}
 
@@ -51,6 +53,8 @@ pub enum UrlencodedError {
     Payload(PayloadError),
 }
 
+impl std::error::Error for UrlencodedError {}
+
 /// Return `BadRequest` for `UrlencodedError`
 impl ResponseError for UrlencodedError {
     fn status_code(&self) -> StatusCode {
@@ -79,6 +83,8 @@ pub enum JsonPayloadError {
     Payload(PayloadError),
 }
 
+impl std::error::Error for JsonPayloadError {}
+
 /// Return `BadRequest` for `JsonPayloadError`
 impl ResponseError for JsonPayloadError {
     fn error_response(&self) -> HttpResponse {
@@ -99,6 +105,8 @@ pub enum PathError {
     Deserialize(serde::de::value::Error),
 }
 
+impl std::error::Error for PathError {}
+
 /// Return `BadRequest` for `PathError`
 impl ResponseError for PathError {
     fn status_code(&self) -> StatusCode {
@@ -114,6 +122,8 @@ pub enum QueryPayloadError {
     Deserialize(serde::de::value::Error),
 }
 
+impl std::error::Error for QueryPayloadError {}
+
 /// Return `BadRequest` for `QueryPayloadError`
 impl ResponseError for QueryPayloadError {
     fn status_code(&self) -> StatusCode {
@@ -139,6 +149,8 @@ pub enum ReadlinesError {
     ContentTypeError(ContentTypeError),
 }
 
+impl std::error::Error for ReadlinesError {}
+
 /// Return `BadRequest` for `ReadlinesError`
 impl ResponseError for ReadlinesError {
     fn status_code(&self) -> StatusCode {