Introduce unit tests (#248)

* Proof-of-concept: unittests

* Add pytest-asyncio dep

* Import Body from stream

* Add test for allow_extra_tracks

* Cleanup decorators

* add test to linting

* fix ruff issues

* Run formatter

* fix

* Dont test every python version

---------

Co-authored-by: Marcus Valtonen Örnhag <marcus.valtonen.ornhag@ericsson.com>
Co-authored-by: Freddy Boulton <alfonsoboulton@gmail.com>

backend/fastrtc/webrtc_connection_mixin.py

@@ -106,6 +106,7 @@ class WebRTCConnectionMixin:
     def clean_up(self, webrtc_id: str):
         self.handlers.pop(webrtc_id, None)
         self.connection_timeouts.pop(webrtc_id, None)
+        self.pcs.pop(webrtc_id, None)
         connection = self.connections.pop(webrtc_id, [])
         for conn in connection:
             if isinstance(conn, AudioCallback):
@@ -229,7 +230,18 @@ class WebRTCConnectionMixin:
                 content={"status": "failed", "meta": {"error": "connection_closed"}},
             )
 
-        if len(self.connections) >= cast(int, self.concurrency_limit):
+        if body["webrtc_id"] in self.connections:
+            return JSONResponse(
+                status_code=200,
+                content={
+                    "status": "failed",
+                    "meta": {
+                        "error": "connection_already_exists",
+                    },
+                },
+            )
+
+        if len(self.pcs) >= cast(int, self.concurrency_limit):
             return JSONResponse(
                 status_code=200,
                 content={