feat: allow connecting to a running kernel from a different browser

This is useful for connecting external devices, such as smartphone or
AR devices (Apple Vision pro and Meta Quest) to the running kernel
using ipypopout.

This is normally not possible since we require the connecting client
to have the same session id as the already kernel.

This this setting, we can disable the session check and the above use
case.

e.g.

SOLARA_KERNEL_SESSION_CHECK=False solara run ...

setting to disable session check

solara/server/kernel_context.py

@@ -383,7 +383,7 @@ def initialize_virtual_kernel(session_id: str, kernel_id: str, websocket: websoc
     if kernel_id in contexts:
         logger.info("reusing virtual kernel: %s", kernel_id)
         context = contexts[kernel_id]
-        if context.session_id != session_id:
+        if solara.server.settings.kernel.session_check and context.session_id != session_id:
             logger.critical("Session id mismatch when reusing kernel (hack attempt?): %s != %s", context.session_id, session_id)
             websocket.send_text("Session id mismatch when reusing kernel (hack attempt?)")
             # to avoid very fast reconnects (we are in a thread anyway)

solara/server/settings.py

@@ -108,6 +108,7 @@ class Kernel(BaseSettings):
     cull_timeout: str = "24h"
     max_count: Optional[int] = None
     threaded: bool = solara.util.has_threads
+    session_check: bool = True
 
     class Config:
         env_prefix = "solara_kernel_"