Oauth: clients & credentials

[taylordowns2000]

Building off #620 , this issue is so that users can create their own Oauth clients (a requirement for folks connecting to Salesforce or MS Dynamics systems, among others) and then create and use Oauth credentials (with user ids, refresh tokens, access tokens, etc.) which make use of those clients.

From #620 - the next steps are:

1. Make some DB changes to allow an oauth_client type of credential
   • two credential types: secrets—or something "standard"—and oauth_client which can have secrets as children.
   • Note that in the current design these clients are credentials and get shared to one or many projects.
   • Note that there should also be an option for a superuser to create an oauth_client which is shared to ALL projects in the instance.
2. Produce a form for creating these Oauth clients.
3. Produce a form for creating a generic Oauth secrets credentials which must be linked to an existing Oauth client.
4. Remove the hard-coded Google Sheets client code to use this new on-demand Oauth client feature.

[mtuchi]

For salesforce adaptor we will have to support both Basic Auth and Oath, I have proposed a new configuration-schema in this issue OpenFn/adaptors#423

This change will a need UI update on lightning credential creation page