Disable "Connect Account" / "Connect" buttons when necessary

[bodom0015]

Problem

The "Connect Account" button is clickable even when there are no more available connections.

Fixes #607

Furthermore, the connect-apikey-modal allows users to submit without entering any/all required fields.

Approach

• Disable "Connect Account" for APIkey providers when user has already added all possible connections
• Disable "Connect" submit button on connect-apikey-modal without user input

How to Test

Preconditions: Remove all Zenodo and/or Dataverse external account connections

1. Checkout and run this branch locally, rebuild the dashboard
2. Login to the WholeTale Dashboard
3. Navigate to the Settings page
4. Beside Dataverse and/or Zenodo, click "Connect Account"
   • The connect-apikey-modal should display
   • The "Connect" button at the bottom=right of the modal should be disable
5. Choose a resource server and enter any value for the API key
   • The "Connect" button should now be enabled
6. Click "Connect" to submit the new API key
   • The modal should close
   • A new entry should appear under the provider indicating that your are now Authorized on... the resource server you just chose
   • A Disconnect button should appear beside the Authorized on... entry
7. Repeat for all Dataverse and/or Zenodo resource servers
   • After adding the last Dataverse and/or Zenodo resource server, you should see that the "Connect Account" button becomes disabled