Provide a dropdown to select params when generating a new token

[chintana-zz]

Description:
Right now, when a user have to generate a new token, all the parameters should be copied from Okta and paste into the form. Since we do know that we're talking to Okta, I think we can provide a drop down with all possible options. Make it easier for end users to select different token types and generate tokens.

Also we can do some validation to make sure users cannot make mistakes. For example, right now when I'm trying to generate a token using client_credentials grant, and provide scope as profile, it gives me following error,

[2019-10-09 14:56:16,647] ERROR - OktaOAuthClient Failed to get accessToken for Consumer Key 0oa1ju03vwiCioUOP357. Response: {"error_description":"Cannot request 'openid' scopes using client credentials.","error":"invalid_scope"}

This error is only visible if you enable debug logs. If you don't enable debug logs it's not possible to see these errors and the UI will not display anything.

Affected Product Version:
OKTA-OAuth-Client-1.0.3-SNAPSHOT.jar (from master)