Reorganize & improve request normalization functions:

* Handle all normalization in `cache_keys` module, get rid of `normalize_dict()` function used in `CachedSession`
* Reorganize `cache_keys` helper functions into the following:
    * `normalize_request()`
        * `normalize_url()`
        * `normalize_headers()`
        * `normalize_params()`
        * `normalize_body()`
        * `normalize_json_body()`
    * `redact_response()`

2 files changed, 8 insertions, 3 deletions

diff --git a/requests_cache/models/__init__.py b/requests_cache/models/__init__.py
index dec305a..6ffc7ad 100644
--- a/requests_cache/models/__init__.py
+++ b/requests_cache/models/__init__.py
@@ -2,11 +2,12 @@
 # flake8: noqa: F401
 from typing import Union
 
-from requests import PreparedRequest, Response
+from requests import PreparedRequest, Request, Response
 
 from .raw_response import CachedHTTPResponse
 from .request import CachedRequest
 from .response import CachedResponse, set_response_defaults
 
 AnyResponse = Union[Response, CachedResponse]
-AnyRequest = Union[PreparedRequest, CachedRequest]
+AnyRequest = Union[Request, PreparedRequest, CachedRequest]
+AnyPreparedRequest = Union[PreparedRequest, CachedRequest]
diff --git a/requests_cache/models/request.py b/requests_cache/models/request.py
index 46951fc..dbeddd0 100644
--- a/requests_cache/models/request.py
+++ b/requests_cache/models/request.py
@@ -1,6 +1,6 @@
 from logging import getLogger
 
-from attr import define, field, fields_dict
+from attr import asdict, define, field, fields_dict
 from requests import PreparedRequest
 from requests.cookies import RequestsCookieJar
 from requests.structures import CaseInsensitiveDict
@@ -27,6 +27,10 @@ class CachedRequest:
         kwargs['cookies'] = getattr(original_request, '_cookies', None)
         return cls(**kwargs)
 
+    def copy(self) -> 'CachedRequest':
+        """Return a copy of the CachedRequest"""
+        return self.__class__(**asdict(self))
+
     def prepare(self) -> PreparedRequest:
         """Convert the CachedRequest back into a PreparedRequest"""
         prepared_request = PreparedRequest()