Better error management as Get-AccessToken was silently failing

[yannick-beot-sp]

If the client id or secret are wrong, we get a strange error about token being null without any debug (because the return was put before the write-debug). By throwing an error, we can see that:

{"error":"invalid_client","error_description":"Bad client credentials"}

• 💄Formatting

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[colin-mckibben-sp]

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