Add dynamic help text for the client_secret field on the application form

[lrq315]

Is your feature request related to a problem? Please describe.

Users may forget to store the client_secret once it is hashed, so it would be helpful to add a warning help text

Describe the solution you'd like

Describe alternatives you've considered

Additional context

[lrq315]

Hi, could you please assign this to me? I have a local implementation ready for review. Thanks!