[REFACTOR]: [Checkout] Remove Default Case Handling

[Sakilmostak]

📝 Feature Description

• We utilize match statements to make pivotal decisions, such as generating requests based on the payment method type and managing responses received from the connector.
• These conditions generally go hand in hand with enum variants.
• Default case is used because a match statement needs to be exhaustive i.e. every variant needs to be covered.
• So, if all the explicit cases are handled then default is used to handle the rest.
• Each connector have these match statements but many of them don’t provide reference to each variant in their default case, rather a _ is put to handle all the other cases.
• This approach carries a risk because developers may inadvertently overlook the need for explicit handling of the new cases.

🔨 Possible Implementation

• Instead of relying on a default match case _, developers should handle each and every variant explicitly.
• By doing so, if there are any changes in the future, they can readily assess the impact of their modifications simply by compiling the code.
• You can check this PR for further reference refactor(connector): [Zen] refactor Zen payment methods not implemented errors #1955

🔖 Note: All the changes needed should be contained within hyperswitch/crates/router/src/connector/

📦 Have you spent some time checking if this feature request has been raised before?

• I checked and didn't find a similar issue

📦 Have you read the Contributing Guidelines?

• I have read the Contributing Guidelines

✨ Are you willing to submit a PR?

[Sakilmostak]

Closed since the required flow is not implemented or already resolved.