Feat: server error - 400 errors / other exceptions during /token

[angela-tran]

Part of #2032

• 400-level error or a non-HTTPError exception during /token returns a JSON response that is used to send user to /error
• /error shows server error template
• Sentry notification is sent
• Analytic event is sent (failed access token request)

Reviewing / testing

To test handling of 400-level HTTP errors, you'll have to force it like in other PRs such as #2089.
To /token, add:

        try:
+          class response:
+             def __init__(self):
+                self.status_code = 400
+
+          raise HTTPError(response=response())
           response = client.request_card_tokenization_access()
        except Exception as e:

To test other exceptions:

• setting an incorrect client_id on PaymentProcessor causes UnsupportedTokenTypeError on client.request_card_tokenization_access
• setting an incorrect api_base_url on PaymentProcessor causes a ConnectionError on client.ensure_active_token
• setting an incorrect client_secret_name on PaymentProcessor could cause an error when creating Client (we read from payment_processor.client_secret_name)

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
benefits/core
views.py
benefits/enrollment
views.py
Project Total

This report was generated by python-coverage-comment-action

[thekaveman]

Very minor request, otherwise this looks good!

[thekaveman]

👍