api: return structured error on unauthorized push

This commit implements a structured error response system for the Ollama API, replacing
ad-hoc error handling and string parsing with proper error types and codes through a new
ErrorResponse struct. Instead of relying on regex to parse error messages for SSH keys,
the API now passes this data in a structured format with standardized fields for error
messages, codes, and additional data. This structured approach makes the API more
maintainable and reliable while improving the developer experience by enabling
programmatic error handling, consistent error formats, and better error
documentation.

api/types.go

@@ -12,27 +12,6 @@ import (
 	"time"
 )
 
-// StatusError is an error with an HTTP status code and message.
-type StatusError struct {
-	StatusCode   int
-	Status       string
-	ErrorMessage string `json:"error"`
-}
-
-func (e StatusError) Error() string {
-	switch {
-	case e.Status != "" && e.ErrorMessage != "":
-		return fmt.Sprintf("%s: %s", e.Status, e.ErrorMessage)
-	case e.Status != "":
-		return e.Status
-	case e.ErrorMessage != "":
-		return e.ErrorMessage
-	default:
-		// this should not happen
-		return "something went wrong, please see the ollama server logs for details"
-	}
-}
-
 // ImageData represents the raw binary data of an image file.
 type ImageData []byte