Refactor job model and optimize job streaming.

Updated the `JobModel` with foreign key relationships and string-based status to enhance database consistency, and improved job event streaming by using `jsonable_encoder` for better serialization. Also, streamlined dependencies by adding `urllib3` to handle HTTP requests.

backend/app/routers/sample.py

@@ -352,7 +352,7 @@ def create_experiment_parameters_for_sample(
 
     new_job = JobModel(
         experiment_parameters_id=new_exp.id,  # <-- Correct reference here
-        parameters=new_exp.to_dict(),  # assuming params has a to_dict() method
+        parameters=new_exp,  # assuming params has a to_dict() method
         status=JobStatus.TODO,
     )
     db.add(new_job)