Fixes session_id passing in agent_openai completion. (#10124)

### What problem does this PR solve?

An exception happens if you give session_id to agent_open_ai completion.
Because session_id is being given as well as **req so it tries to send
session_id twice. But also the logic seemed odd on picking one of
session_id, id, metadata.id. So cleaned it up a little.

See #10111 

### Type of change

- [X] Bug Fix (non-breaking change which fixes an issue)

api/apps/sdk/session.py

@@ -414,7 +414,7 @@ def agents_completion_openai_compatibility(tenant_id, agent_id):
                 tenant_id,
                 agent_id,
                 question,
-                session_id=req.get("session_id", req.get("id", "") or req.get("metadata", {}).get("id", "")),
+                session_id=req.pop("session_id", req.get("id", "")) or req.get("metadata", {}).get("id", ""),
                 stream=True,
                 **req,
             ),
@@ -432,7 +432,7 @@ def agents_completion_openai_compatibility(tenant_id, agent_id):
                 tenant_id,
                 agent_id,
                 question,
-                session_id=req.get("session_id", req.get("id", "") or req.get("metadata", {}).get("id", "")),
+                session_id=req.pop("session_id", req.get("id", "")) or req.get("metadata", {}).get("id", ""),
                 stream=False,
                 **req,
             )