Search SEC EDGAR filings using the full-text search API

Verified steps

1. No API key is required for the official SEC EDGAR full-text search endpoint; send a GET request to https://efts.sec.gov/LATEST/search-index?q={query}&dateRange=custom&startdt={YYYY-MM-DD}&enddt={YYYY-MM-DD} to search filing text.
2. Use the forms parameter to restrict results to specific form types (e.g., forms=10-K,10-Q) and the entity parameter to filter by company name or CIK.
3. Parse the JSON response hits array; each hit contains the filing accession number, form type, company name, CIK, and a text snippet; use the accession number to construct the filing document URL at https://www.sec.gov/Archives/edgar/data/{CIK}/{accession-no-dashes}/.
4. Retrieve the full filing index by fetching https://data.sec.gov/submissions/CIK{CIK-zero-padded}.json for a specific company to list all filings and their document paths.
5. Respect the SEC rate limit of 10 requests per second across all EDGAR endpoints; exceeding this limit triggers a temporary IP block of approximately 10 minutes — implement a request throttle.
6. Set a User-Agent header on every request in the format your-name your-email@example.com per the SEC's published fair-use policy; requests without a valid User-Agent may be blocked.