Admin user can add unsupported toleration to notebook pods; spawning is impossible until toleration is changed

Description of problem:

In the new Admin UI to set notebook tolerations (RHODS-3624) an admin user is able to add an unsupported toleration (e.g. "TestToleration, AndAnotherKey"). The setting can be saved as is.
Trying to spawn notebooks after this setting has been saved will become impossible (the modal will show no progress in the loading bar) but no error message is shown to the user.
Looking into the logs of the `notebook-controller-deployment` we can see this error:

1.6617843718307014e+09
	DEBUG	events	Warning	{"object": 
{"kind":"Notebook","namespace":"rhods-notebooks","name":"jupyter-nb-ldap-2dadmin4","uid":"d30182b5-c9b5-4d66-8815-9359b6484a20","apiVersion":"kubeflow.org/v1beta1","resourceVersion":"334720"},
 "reason": "FailedCreate", "message": "Reissued from 
statefulset/jupyter-nb-ldap-2dadmin4: create Pod 
jupyter-nb-ldap-2dadmin4-0 in StatefulSet jupyter-nb-ldap-2dadmin4 
failed error: Pod \"jupyter-nb-ldap-2dadmin4-0\" is invalid: 
spec.tolerations[0].key: Invalid value: \"TestToleration, 
AndAnotherKey\": name part must consist of alphanumeric characters, '-',
 '_' or '.', and must start and end with an alphanumeric character (e.g.
 'MyName',  or 'my.name',  or '123-abc', regex used for validation is 
'([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9]')"} 

Important part being:

Pod \"jupyter-nb-ldap-2dadmin4-0\" is invalid: spec.tolerations[0].key: Invalid value: \"TestToleration, AndAnotherKey\": name part must consist of alphanumeric characters, '-', '_' or '.', and must start and end with an alphanumeric character (e.g. 'MyName', or 'my.name', or '123-abc', regex used for validation is '([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9]') 

The only way to fix the issue is to remove (or update) the toleration from the admin UI to something that is allowed by openshift.

Prerequisites (if any, like setup, operators/versions):

Latest rhods 1.16 live build (quay.io/llasmith/odh-operator-container-live:1.16.0-dashboard-kfnbc)

Steps to Reproduce

1. Log in as rhods admin
2. Go to Cluster settings in RHODS dashboard
3. Add a toleration that is unsupported by openshift
4. Save the toleration
5. Try spawning notebooks

Actual results:

User is able to save the setting with an unsupported toleration

Spawning is impossible but no error message is shown to the user

Expected results:

User should not be allowed to set an unsupported toleration

Meaningful error message should be shown to the user in order to be able to fix the problem without having to look in the logs of a pod

Reproducibility (Always/Intermittent/Only Once):

always

Build Details:

Workaround:

Additional info: