refactor: Introduce standardized API error

This commit refactors the application's error handling mechanism by introducing a new standardized error type, `types.NewAPIError`. It also renames common JSON utility functions for better clarity.

Previously, internal error handling was tightly coupled to the `dto.OpenAIError` format. This change decouples the internal logic from the external API representation.

Key changes:
- A new `types.NewAPIError` struct is introduced to serve as a canonical internal representation for all API errors.
- All relay adapters (OpenAI, Claude, Gemini, etc.) are updated to return `*types.NewAPIError`.
- Controllers now convert the internal `NewAPIError` to the client-facing `OpenAIError` format at the API boundary, ensuring backward compatibility.
- Channel auto-disable/enable logic is updated to use the new standardized error type.
- JSON utility functions are renamed to align with Go's standard library conventions (e.g., `UnmarshalJson` -> `Unmarshal`, `EncodeJson` -> `Marshal`).

common/gin.go

@@ -32,7 +32,7 @@ func UnmarshalBodyReusable(c *gin.Context, v any) error {
 	}
 	contentType := c.Request.Header.Get("Content-Type")
 	if strings.HasPrefix(contentType, "application/json") {
-		err = UnmarshalJson(requestBody, &v)
+		err = Unmarshal(requestBody, &v)
 	} else {
 		// skip for now
 		// TODO: someday non json request have variant model, we will need to implementation this

common/json.go

@@ -5,7 +5,7 @@ import (
 	"encoding/json"
 )
 
-func UnmarshalJson(data []byte, v any) error {
+func Unmarshal(data []byte, v any) error {
 	return json.Unmarshal(data, v)
 }
 
@@ -17,6 +17,6 @@ func DecodeJson(reader *bytes.Reader, v any) error {
 	return json.NewDecoder(reader).Decode(v)
 }
 
-func EncodeJson(v any) ([]byte, error) {
+func Marshal(v any) ([]byte, error) {
 	return json.Marshal(v)
 }

common/str.go

@@ -33,7 +33,7 @@ func MapToJsonStr(m map[string]interface{}) string {
 
 func StrToMap(str string) (map[string]interface{}, error) {
 	m := make(map[string]interface{})
-	err := UnmarshalJson([]byte(str), &m)
+	err := Unmarshal([]byte(str), &m)
 	if err != nil {
 		return nil, err
 	}