[kitsune] Update enriched fields

[jjmerchante]

This PR allows to execute the demography study for Kitsune backend.

The enriched index now includes a unique identifier for questions and answers (id), this was causing an error when trying to autorefresh because uuid was missing.

Include the default raw fields in answers items that were missing: metadata__updated_on , metadata__timestamp, offset, origin, tag, and uuid.

[coveralls]

Pull Request Test Coverage Report for Build 8230580222

Details

• 7 of 7 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 85.561%

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Totals
Change from base Build 8112037918:	0.02%
Covered Lines:	7472
Relevant Lines:	8733

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💛 - Coveralls