Fix support for Redis Unix-Domainsocket-connections (#5214)

### Motivation

I usually use Redis with UnixDomainsocket-connections, using
connection-URLs beginning with `unix://`. When trying to use this for
persistence in NiceGUI I discovered, that this throws the error 'Could
not load data from Redis with key ...'. The reason is, that the option
`socket_keepalive` is not present when `redis.from_url()` leads to the
use of Redis' class `UnixDomainSocketConnection`.

### Implementation

The fix builds a connection-parameter-dict in the class
`RedisPersistentDict` and adds the option 'socket_keepalive' ony when
the URL is not beginning with `unix://`. Furthermore it reuses this dict
for the Redis-connection in the same Class on `initialize_sync()`.

### Progress

- [x] I chose a meaningful title that completes the sentence: "If
applied, this PR will..."
- [x] The implementation is complete.
- [x] Pytests are are not necessary.
- [x] Documentation is not necessary.

---------

Co-authored-by: Rodja Trappe <rodja@zauberzeug.com>
Co-authored-by: Falko Schindler <falko@zauberzeug.com>

Author: 3 people

nicegui/persistence/redis_persistent_dict.py

@@ -17,13 +17,13 @@ def __init__(self, *, url: str, id: str, key_prefix: str = 'nicegui:') -> None:
         if not optional_features.has('redis'):
             raise ImportError('Redis is not installed. Please run "pip install nicegui[redis]".')
         self.url = url
-        self.redis_client = redis.from_url(
-            url,
-            health_check_interval=10,
-            socket_connect_timeout=5,
-            retry_on_timeout=True,
-            socket_keepalive=True,
-        )
+        self._redis_client_params = {
+            'health_check_interval': 10,
+            'socket_connect_timeout': 5,
+            'retry_on_timeout': True,
+            **({'socket_keepalive': True} if not url.startswith('unix://') else {}),
+        }
+        self.redis_client = redis.from_url(self.url, **self._redis_client_params)
         self.pubsub = self.redis_client.pubsub()
         self.key = key_prefix + id
         self._should_listen = True
@@ -40,13 +40,7 @@ async def initialize(self) -> None:
 
     def initialize_sync(self) -> None:
         """Load initial data from Redis and start listening for changes in a synchronous context."""
-        with redis_sync.from_url(
-            self.url,
-            health_check_interval=10,
-            socket_connect_timeout=5,
-            retry_on_timeout=True,
-            socket_keepalive=True,
-        ) as redis_client_sync:
+        with redis_sync.from_url(self.url, **self._redis_client_params) as redis_client_sync:
             try:
                 data = redis_client_sync.get(self.key)
                 self.update(json.loads(data) if data else {})