Updated multiple models to include handling ledger_xid. Renamed views from EntityModelDetailView to EntityModelDetailHandlerView and updated its references. Also, updated migrations to fit the changes in models. Made improvements in ledger URL handling and related permissions for superusers.

Implement IOCursor modes and enhance data validation

The commit introduces the concept of IOCursor modes in the project. It now allows for operation either in STRICT or PERMISSIVE modes. STRICT mode denies commitment of transactions to non-existing ledgers while PERMISSIVE mode allows it.

Changes also include enhanced data validation to prevent transactions on locked accounts, added filters for locked/unlocked and active accounts, and implemented a method to retrieve transactionable accounts. Other updates include changes to TransactionModel manager class and added create/update timestamps in Ledger admin view.