New descriptions and examples across the API reference

Broker API

Adds missing descriptions and examples to the Broker API reference and corrects how several documented fields render. Request and response shapes are unchanged.

• Documents the request body for creating a signed agreement.
• Adds an example for the idempotency key conflict error on journal creation.
• Adds examples for JITReportDownloadURL fields on JIT reports.
• Adds a description and examples for PortfolioHistoryError.
• Adds an example for account_sub_type on AccountCreationRequest.
• Fixes rendering so the correct descriptions and defaults appear for account_type, account_sub_type, and minor_identity on AccountCreationRequest, securities on the ACATS transfer details, travel_rule_info on WhitelistedAddress, and the ACATS pagination tokens.
• The deprecation notices for belongs_to and created_by on the admin action event schema are now visible, and their descriptions no longer repeat the deprecation reason.

Affected Endpoints

• POST /v1/agreements
• POST /v1/journals
• POST /v1/accounts
• POST /v1beta1/acats/{account_id}
• GET /v2/events/admin-actions
• GET /v1/transfers/jit/reports
• GET /v1/trading/accounts/{account_id}/account/portfolio/history
• POST /v1/accounts/{account_id}/wallets/whitelists
• GET /v1/accounts/{account_id}/wallets/whitelists

Trading API

Adds missing descriptions and examples to the Trading API reference. Request and response shapes are unchanged.

• Adds a response example for the PortfolioHistory schema.
• Adds a description and examples for PortfolioHistoryError.
• Fixes rendering so the documented description for travel_rule_info on WhitelistedAddress appears.

Affected Endpoints

• GET /v2/account/portfolio/history
• POST /v2/wallets/whitelists
• GET /v2/wallets/whitelists