Currently, only the OAuth2 Authorization Code grant type flow is
supported. Upcoming SaaS connectors require more flexibility & can use
different OAuth2 grant type flows. For example, the Genesys connector
needs a user-configured domain to perform authentication and get an
access token. Our current OAuth2 framework only supports access token
URLs that don't contain user-configured values, and adding that support
would be a larger effort than we want to take on right now. With the
Client Credentials grant type flow, we can inject a user-configured
value in the access token URL at runtime to support this use case.

This is a minimal connector for Genesys, containing just the `users`
and `conversations` streams.

`users` is a simple snapshot since there is no way to request updated
users.

`conversations` is incremental and leverage two different endpoints. A
real-time endpoint is used to get created conversations incrementally.
This real-time endpoint is not appropriate to get updates
(we can only specify time ranges for created conversations), so we also
attempt to use the delayed, asynchronous analytics job endpoint to get
conversations that have ended in the last day. This is not meant to
capture all ended conversations as there are scenarios where we would
miss capturing these updates (ex: no conversations are created for a
while but conversations are ended), and a backfill will be required to
fully capture all ended conversations.

The code for retrieving conversations in real-time from the query
endpoint is left in the previous commit in case we want to add this
functionality later when the CDK has the capability to have a delayed
stream / a second cursor.