Add unique constraint to external_filing_id, registry_code

[aaroncameron-wk]

Note: I haven't been able to confirm if any duplicates already exist in the production database. We should wait to deploy this until we've either confirmed that no duplicates exist, or until a window where potential downtime would not have a large impact on users.

Reason for change

Two instances of the server can briefly be running (and performing indexing on the stream) simultaneously. This could result in duplicate filings being indexed.

Description of change

• Add unique index to prevent duplicate filing entries
• Warn on violation of unique index
• Add additional delay before stream indexing to minimize instance overlap

Steps to Test

Locally, run two instances of the server simultaneously. Confirm warning eventually appears for duplicate filing entry.

review:
@Arelle/arelle