Upgrade TransactionHandler: Improve readability and error handling

[bhaskar-allam]

Simplified the String() method for TransactionHandlerType:

• Removed the error return, as it's not necessary for a String() method.
• Used a switch statement without fallthrough for better readability.
• Added a named error ErrInvalidTransactionHandlerType for better error handling.

Improved the Call method:

• Used make to pre-allocate the values slice with a capacity of 2.
• Renamed someResp to response for better clarity.

Refactored the NewTransactionHandler function:

• Extracted the validation logic into a separate validateTransactionHandler function for better readability and maintainability.
• Used fmt.Errorf with %w to wrap the error and provide more context.

Improved error messages:

• Used errors.New for static error messages.

• Used fmt.Errorf for dynamic error messages.

• Updated the struct initialization in NewTransactionHandler to use field names for better clarity.

Signed-off-by: Bhaskar Allam bhaskar.ram@linux.com

[bestbeforetoday]

Since the code doesn't look to use the error return value from TransactionHandlerType.String(), removing it seems reasonable. However, you have not updated the accompanying unit tests so the project will no longer build

[bhaskar-allam]

I should update transaction_handler_test.go also and run Unit Tests againest transaction_handler.go , right ?