[BE] Create microservice to provide current exchange rate info

[Eugeniosales]

Description:

Create job to provide current exchange rate info from the ExchangeRate table in DynamoDB.

Acceptance criteria:

• Add lambda getExchangeRate of ExchangeRate domain
• Add unit test to business and adapters layer
• Create private subnets in two availability zones
• Create Application Load Balancer and attach to private subnets
• Attach lambda to private subnets

[Eugeniosales]

Exemplo de resposta:

{
    "success": true,
    "timestamp": 1519296206,
    "baseCurrency": "EUR",
    "date": "2021-03-17",
    "rates": {
        "AUD": 1.566015,
        "CAD": 1.560132,
        "CHF": 1.154727,
        "CNY": 7.827874,
        "GBP": 0.882047,
        "JPY": 132.360679,
        "USD": 1.23396,
    [...]
    }
}