refactor(connector): added amount conversion framework for Mifinity

[KiranKBR]

Type of Change

• Refactoring

Description

This PR do amount conversion changes for Mifinity Connector and it accepts the amount in StringMajorUnit

Additional Changes

• This PR modifies the API contract
• This PR modifies the database schema
• This PR modifies application configuration/environment variables

Motivation and Context

https://github.com/juspay/hyperswitch-cloud/issues/6148

How did you test it?

Payment Request:

curl --location 'http://localhost:8080/payments' \
--header 'Content-Type: application/json' \
--header 'Accept: application/json' \
--header 'api-key: dev_WRjhnbKDoMkMK2LlnwS2EDjEP0wMGhJPgOOk1lPrQybpvCVcLVOLcNpATsbIzruw' \
--data-raw '{
    "amount": 1000,
    "currency": "EUR",
    "confirm": true,
    "capture_method": "automatic",
    "capture_on": "2022-09-10T10:11:12Z",
    "amount_to_capture": 1000,
    "customer_id": "StripeCustomer",
    "email": "guest@example.com",
    "name": "John Doe",
    "phone": "999999999",
    "phone_country_code": "+1",
    "description": "Its my first payment request",
    "authentication_type": "no_three_ds",
    "return_url": "https://www.google.com/",
    "payment_method": "wallet",
    "payment_method_type": "mifinity",
    "payment_method_data": {
        "wallet": {
            "mifinity": {
                "destination_account_number": "5001000001223369",
                "date_of_birth": "2001-10-16"
            }
        }
    },
    "billing": {
        "address": {
            "line1": "1467",
            "line2": "Harrison Street",
            "line3": "Harrison Street",
            "city": "San Fransico",
            "state": "California",
            "zip": "94122",
            "country": "DE",
            "first_name": "joseph",
            "last_name": "Doe"
        },
        "phone": {
            "number": "8056594427",
            "country_code": "+91"
        },
        "email": "swangi@gmail.com"
    },
    "shipping": {
        "address": {
            "line1": "1467",
            "line2": "Harrison Street",
            "line3": "Harrison Street",
            "city": "San Fransico",
            "state": "California",
            "zip": "94122",
            "country": "DE",
            "first_name": "joseph",
            "last_name": "Doe"
        },
        "phone": {
            "number": "8056594427",
            "country_code": "+91"
        }
    },
    "statement_descriptor_name": "joseph",
    "statement_descriptor_suffix": "JS",
    "metadata": {
        "udf1": "value1",
        "new_customer": "true",
        "login_date": "2019-09-10T10:11:12Z"
    }  
}'

Checklist

• I formatted the code cargo +nightly fmt --all
• I addressed lints thrown by cargo clippy
• I reviewed the submitted code
• I added unit tests for my changes where possible