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/client.go

@@ -163,24 +163,29 @@ func (c *Client) stream(ctx context.Context, method, path string, data any, fn f
 	scanBuf := make([]byte, 0, maxBufferSize)
 	scanner.Buffer(scanBuf, maxBufferSize)
 	for scanner.Scan() {
-		var errorResponse struct {
-			Error string `json:"error,omitempty"`
-		}
-
 		bts := scanner.Bytes()
+
+		var errorResponse ErrorResponse
 		if err := json.Unmarshal(bts, &errorResponse); err != nil {
 			return fmt.Errorf("unmarshal: %w", err)
 		}
 
-		if errorResponse.Error != "" {
-			return errors.New(errorResponse.Error)
+		switch errorResponse.Code {
+		case ErrCodeUnknownKey:
+			return ErrUnknownOllamaKey{
+				Message: errorResponse.Message,
+				Key:     errorResponse.Data["key"].(string),
+			}
+		}
+		if errorResponse.Message != "" {
+			return errors.New(errorResponse.Message)
 		}
 
 		if response.StatusCode >= http.StatusBadRequest {
 			return StatusError{
 				StatusCode:   response.StatusCode,
 				Status:       response.Status,
-				ErrorMessage: errorResponse.Error,
+				ErrorMessage: errorResponse.Message,
 			}
 		}