[Task]: Add original_close_date + original_close_date description to the get opportunity endpoint

[acouch]

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Migrated from navapbc#66
Originally created by @chouinar on Fri, 31 May 2024 14:05:54 GMT

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Summary

Logic from the legacy system:

• Only synopsis records (forecasts have no close date themselves)
• If the revision number is null or 0, it assumes its the earliest, and returns that.
• Otherwise finds the earliest history synopsis record and returns its close date.

Acceptance criteria

No response