HPO doesn't throw any error on passing an empty string

[chandrams]

Passing an empty string to some of the fields (experiment_id, trial_result, result_value_type) in the HPO experiment or results json doesn't throw any error message.

To recreate the issue:

• Run ./deploy_hpo.sh -c native
• Post the experiment json using the curl command
• Below is an example curl command to post an experiment with empty string for experiment_id

curl -s -H 'Content-Type: application/json' http://localhost:8085/experiment_trials -d '{"operation":"EXP_TRIAL_GENERATE_NEW","search_space":{"experiment_name":"petclinic-sample-2-75884c5549-npvgd","total_trials":5,"parallel_trials":1,"experiment_id":" ","value_type":"double","hpo_algo_impl":"optuna_tpe","objective_function":"transaction_response_time","tunables":[{"value_type":"double","lower_bound":150,"name":"memoryRequest","upper_bound":300,"step":1},{"value_type":"double","lower_bound":1,"name":"cpuRequest","upper_bound":3,"step":0.01}],"slo_class":"response_time","direction":"minimize"}}'

[chandrams]

There are other scenarios that do not throw any error messages:

• Pass an invalid experiment id
• Pass an invalid searchspace - Tested it with just a couple of paraeters (direction & slo_class) by passing invalid values