[DOCUSIGN] Paid integration

Hello,

Thanks for your time, and effort to make this software.

We wanted to be able to request signature from pdf document via nextcloud. I have see the Integration provided here and at forst it seem to work.
Creating a develloper account, adding an App in App & Keys. Pasting value and saving them in nextcloud worked like a charm.

We have made test and it work like we intended to have it, so we followed the process to "GoLive".

Here documentation is laking, but we managed to have an account with a paid API Plan.

Once the app is live you have to : https://developers.docusign.com/docs/esign-rest-api/go-live/after-go-live/

Defining OAuth settings for production
So same app key but new secret.

Using production API endpoints
Here I had to go to : https://github.com/nextcloud/approval/blob/e9d2b5588adc8e4409127853552458d60aa9dcb5/lib/AppInfo/Application.php#L48-L49
And remove the -d from the domain.
And go to : https://github.com/nextcloud/approval/blob/e9d2b5588adc8e4409127853552458d60aa9dcb5/js/approval-adminSettings.js#L2
To do the same.

Without those modification I wasn't able to login as production account so requested sign where non valid.
Here was the log : 400 Bad Request response: {"error":"invalid_grant","error_description":"unauthorized_client"

Maybe we should have in admin, a check box to switch between production and devellopment.

if productionAccount === true { baseDomain = account } else { baseDomain = account-d }

Start by reading lib/AppInfo/Application.php around the production API domain and js/approval-adminSettings.js around the client domain, as linked in the issue. Add an admin setting to select development or production endpoints, then verify that production login and signature requests use the production domain instead of the -d domain.