Some serialization fixes & updates:

* Fix tests on python 3.6:
    * Make `cattrs` optional again
    * Don't run tests for serializers with missing optional dependencies
    * Show any skipped tests in pytest output
 * Fix redirect serialization for backends that serialize all values (DynamoDB and Redis)
    * Otherwise, the redirect value (which is just another key) will get converted into a `CachedResponse`
* Make `pickle` serializer use `cattrs` if installed
* Make `bson` serializer compatible with both `pymongo` version and standalone `bson` library
* Split up `CattrStage` and preconf converters into separate modules
* Turn preconf converters into `Stage` objects
* Add `DeprecationWarning` for previous method of using `itsdangerous`, now that there's a better way to initialize it via `SerializerPipeline`
* Remove `suppress_warnings` kwarg that's now unused
* Make `SerializerPipeline`, `Stage`, and `CattrStage` importable from top-level package (`from requests_cache import ...`)
* Add some more details to docs and docstrings

1 files changed, 1 insertions, 0 deletions

diff --git a/pyproject.toml b/pyproject.toml
index 2f553c1..b1c38fb 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -27,6 +27,7 @@ requests = "^2.17"
 url-normalize = "^1.4"
 
 # Optional serialization dependencies
+# Note: cattrs will be a hard dependency in a future release, after dropping python 3.6 support
 bson = {version = ">=0.5", optional = true}
 cattrs = {version = "^1.7", python = "^3.7", optional = true}
 ujson = {version = ">=4.0", optional = true}