Final integration tweaks with detector lambda

[matt-bernhardt]

Developer

Now that the detector lambda has been deployed and can do real work, it seems like some last-minute tweaks are needed for TACOS to communicate reliably.

How does this address that need:

Three small tweaks are needed to Detector::MlCitation:

1. Add a Content-Type header to the communication with the detector
2. Sort and re-hash the hash of features (the order of parameters matters for scikit-learn)
3. The response parsing in the fetch method needs to account for a capitalized response "True" instead of "true".

Document any side effects to this change:

Along with these changes comes a few tweaks around the tests.

• Making sure we explicitly test for both responses via the .new() method
• Setting the sequence test to use its own cassette with multiple interactions (avoids a first-time-through test failure when renegenerating cassettes)
• Scrubbing the challenge secret from cassettes as a defense in depth
• Regenerating all cassettes

Ticket(s)

https://mitlibraries.atlassian.net/browse/TCO-187

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