Enhance FindOrCreatePayer performance

[fbac]

Update FindOrCreatePayer query to use a union CTE for id selection to improve performance in payer_reports.sql and regenerate payer_reports.sql.go

Add CTE u that unions ins and existing payer lookup, and change the final select to SELECT id FROM u LIMIT 1 in payer_reports.sql; regenerate corresponding code in payer_reports.sql.go.

📍Where to Start

Start with the FindOrCreatePayer SQL in payer_reports.sql, then review the generated changes in payer_reports.sql.go.

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Macroscope summarized 4b0ae57.