BE should not return secrets to FE

[ebb-tide]

Requirements for this:

• discuss with @ebb-tide what FE wants here

Original issue:

Notification Endpoints have fields that contain secrets. 
These fields should not be returned in plain text. 
Let's discuss some way the FE can know that these fields have been set. 

[imogenkinsman]

I've checked, and the API is not returning the secret; it's responding with mapping information.

It shouldn't be returning anything (and we should def fix this) but we could punt on fixing this this week if needed.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically closed because it has not had recent activity. Please reopen if this issue is still important to you. Thank you for your contributions.