feat(rules): add post-request rules system with response manipulation (#160)

* Add comprehensive post-request rules support for response phase
* Enable response body, status, and header manipulation via set commands
* Refactor command handlers to support both request and response phases
* Implement response modifier system for post-request template execution
* Support response-based rule matching with status and header checks
* Add comprehensive benchmarks for matcher performance
* Refactor authentication and proxying commands for unified error handling
* Support negated conditions with !
* Enhance error handling, error formatting and validation
* Routes: add `rule_file` field with rule preset support
* Environment variable substitution: now supports variables without `GODOXY_` prefix

* new conditions:
  * `on resp_header <key> [<value>]`
  * `on status <status>`
* new commands:
  * `require_auth`
  * `set resp_header <key> <template>`
  * `set resp_body <template>`
  * `set status <code>`
  * `log <level> <path> <template>`
  * `notify <level> <provider> <title_template> <body_template>`

internal/logging/accesslog/file_logger.go

@@ -26,7 +26,10 @@ var (
 	openedFilesMu sync.Mutex
 )
 
-func newFileIO(path string) (WriterWithName, error) {
+// NewFileIO creates a new file writer with cleaned path.
+//
+// If the file is already opened, it will be returned.
+func NewFileIO(path string) (WriterWithName, error) {
 	openedFilesMu.Lock()
 	defer openedFilesMu.Unlock()