Add feature for manually exchange an authorization code for a token

[acoumb]

Current PR adds a feature to the HubSpot Forms integration that allow users to manually exchange an authorization code for an access token.

A particular use case has created an issue during the OAuth2 flow. When connecting to the service without having any cookie credentials of that service, the browser removes the window.opener property resulting in the authorization window not closing and an inability to retrieve the access token.

To address this, we are watching the window for 7 seconds, and if it remains open, we are displaying an input field allowing users to exchange the authorization code for an access token.

A small demo here.

Next steps will be to apply the same change to Dynamics and Google.