Adds support for the Content-Encoding header

[aminroosta]

Fixes #255

[nicolasff]

Hi Amin, thanks for the PR! I've only given it a brief look so far but will spend some time on it today.

In the meantime I did trigger the tests which run on a range of systems, they're all marked as failed simply because the same test failed in all environments; so it looks all red but it is really just about one test :-)

From the output:

FAIL: test_encoding (__main__.TestJSON.test_encoding)
success type (+OK)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/__w/webdis/webdis/./tests/basic.py", line 87, in test_encoding
    self.assertTrue(f.getheader('ETag') == '"fcb2917ae[14](https://github.com/nicolasff/webdis/actions/runs/13878036214/job/38846608045?pr=256#step:9:15)a62e911fbfb2b8ea66800"')
AssertionError: False is not true

To run this validation yourself, start Webdis with websockets enabled (set "websockets": true in webdis.json):

-  "websockets": false,
+  "websockets": true,

and in the tests/ directory run ./basic.py and ./ws-tests.py, that's usually how I run an initial check over Webdis.

You'll need to install websocket-client>=1.1.0 for Python, I suggest you create a venv to leave your global Python install untouched. With Redis and Webdis already running:

cd tests
python -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt

./basic.py
./ws-tests.py

[aminroosta]

Hello @nicolasff, I appreciate you taking the time to review the PR.
I've made a tiny change in ec025f8 to support both key.json.gzip and key.gzip.
I hope the pointer arithmetic is accurate 🤞.

[aminroosta]

Will fix the unit tests later today. The python gzip implementation includes a timestamp.

[aminroosta]

Done.