Updates to transaction API endpoints

Affected endpoints and objects
- The create a transaction, list transactions, find a specific transaction, and find a specific transaction by external ID endpoint responses, webhook event objects, and API Co-Signer callback objects are now in a clearer order and descriptions of most fields are improved.
The TransactionOperation data object now includes all options with a detailed description of each one.
The feePayerInfo field has been removed from the documentation. It was included in the Developer Documentation but has never been returned in any response.
Known limitations
The following limitations are known for the following cases:
- When creating a transaction, if the forceSweep parameter is set to true for a transfer when the source account is 1 DOT, the transaction will fail. Any amount more or less than 1 DOT succeeds. This is a Polkadot blockchain limitation.
- When retrieving transactions, if a transaction uses the destinations object with more than one value in the array, the blockInfo data object is returned as null.
Compound
The SUPPLY_FROM_COMPOUND and REDEEM_FROM_COMPOUND transaction operation have been removed from the documentation.
These options are deprecated and no longer available when creating a transaction. They are still returned when retrieving relevant past transactions.
Recommended numeric string fields
Several numeric fields have been deprecated. Although they are still supported, they are now replaced by numeric string fields that are highly recommended and allow greater accuracy. The deprecated fields and the recommended amountInfo object that replaces them are described below.
The amountInfo object is now recommended
The amount, requestedAmount, netAmount, and amountUSD numeric fields have been deprecated for all Transaction Response objects. The deprecated fields are still returned in all relevant responses but are not recommended. The amountInfo object that was introduced in September 2020, includes all these fields as strings and is recommended in place. These string fields ensure support for accurate decimal precision.
- The amountInfo object comprises the following fields:
  - amount - string
    If the transfer is a withdrawal from an exchange, the actual amount that was requested to be transferred. Otherwise, it is the requested amount. This value will always be equal to the amount (number) parameter of TransactionDetails.
  - requestedAmount - string
    The amount requested by the user.
  - netAmount - string
    The net amount of the transaction, after fee deduction.
  - amountUSD - string
    The USD value of the requested amount.