feat(op): user slog for logging

integrate with golang.org/x/exp/slog for logging.
provide a middleware for request scoped logging.

BREAKING CHANGES:

1. OpenIDProvider and sub-interfaces get a Logger()
method to return the configured logger;
2. AuthRequestError now takes the complete Authorizer,
instead of only the encoder. So that it may use its Logger() method.
3. RequestError now takes a Logger as argument.

pkg/oidc/authorization.go

@@ -1,5 +1,11 @@
 package oidc
 
+import (
+	"fmt"
+
+	"golang.org/x/exp/slog"
+)
+
 const (
 	// ScopeOpenID defines the scope `openid`
 	// OpenID Connect requests MUST contain the `openid` scope value
@@ -86,6 +92,15 @@ type AuthRequest struct {
 	RequestParam string `schema:"request"`
 }
 
+func (a *AuthRequest) LogValue() slog.Value {
+	return slog.GroupValue(
+		slog.Any("scopes", fmt.Stringer(a.Scopes)),
+		slog.String("response_type", string(a.ResponseType)),
+		slog.String("client_id", a.ClientID),
+		slog.String("redirect_uri", a.RedirectURI),
+	)
+}
+
 // GetRedirectURI returns the redirect_uri value for the ErrAuthRequest interface
 func (a *AuthRequest) GetRedirectURI() string {
 	return a.RedirectURI

pkg/oidc/error.go

@@ -3,6 +3,8 @@ package oidc
 import (
 	"errors"
 	"fmt"
+
+	"golang.org/x/exp/slog"
 )
 
 type errorType string
@@ -171,3 +173,31 @@ func DefaultToServerError(err error, description string) *Error {
 	}
 	return oauth
 }
+
+func (e *Error) LogLevel() slog.Level {
+	level := slog.LevelWarn
+	if e.ErrorType == ServerError {
+		level = slog.LevelError
+	}
+	if e.ErrorType == AuthorizationPending {
+		level = slog.LevelInfo
+	}
+	return level
+}
+
+func (e *Error) LogValue() slog.Value {
+	attrs := make([]slog.Attr, 0, 4)
+	if e.Parent != nil {
+		attrs = append(attrs, slog.Any("parent", e.Parent))
+	}
+	if e.Description != "" {
+		attrs = append(attrs, slog.String("description", e.Description))
+	}
+	if e.ErrorType != "" {
+		attrs = append(attrs, slog.String("type", string(e.ErrorType)))
+	}
+	if e.State != "" {
+		attrs = append(attrs, slog.String("state", e.State))
+	}
+	return slog.GroupValue(attrs...)
+}

pkg/oidc/types.go

@@ -106,7 +106,7 @@ type ResponseType string
 
 type ResponseMode string
 
-func (s SpaceDelimitedArray) Encode() string {
+func (s SpaceDelimitedArray) String() string {
 	return strings.Join(s, " ")
 }
 
@@ -116,11 +116,11 @@ func (s *SpaceDelimitedArray) UnmarshalText(text []byte) error {
 }
 
 func (s SpaceDelimitedArray) MarshalText() ([]byte, error) {
-	return []byte(s.Encode()), nil
+	return []byte(s.String()), nil
 }
 
 func (s SpaceDelimitedArray) MarshalJSON() ([]byte, error) {
-	return json.Marshal((s).Encode())
+	return json.Marshal((s).String())
 }
 
 func (s *SpaceDelimitedArray) UnmarshalJSON(data []byte) error {
@@ -165,7 +165,7 @@ func (s SpaceDelimitedArray) Value() (driver.Value, error) {
 func NewEncoder() *schema.Encoder {
 	e := schema.NewEncoder()
 	e.RegisterEncoder(SpaceDelimitedArray{}, func(value reflect.Value) string {
-		return value.Interface().(SpaceDelimitedArray).Encode()
+		return value.Interface().(SpaceDelimitedArray).String()
 	})
 	return e
 }