XDRill: LedgerEntryChange level functions

[chowbao]

The LedgerEntryChange level functions is similar to the account_entry.go example code from the design doc

Creating the LedgerEntryChange level functions is probably more involved than the other levels because of the considerate amount of overlapping data field names between different entry types.

• Create new struct for the Operation level functions

  type Change struct {
    Change ingest.Change
  }
  

• Create function to GetLedgerEntryChanges() or just use the LedgerChangeReader()

• Define functions needed for

  • accounts
  • account_signers
  • claimable_balances
  • config_settings
  • contract_code
  • contract_data
  • offers
  • trustlines
  • ttl

• It may be worth exploring Change specific structs and low level helper functions rather than combining all ledger change types into a single Change struct