Option to use dotenv instead of assigning Environment Variables

[nhall-tink]

Nodejs gives us a way to load config files into the project using dotenv.

This is to give the option to use the dotenv file, meaning that there are no system level changes needed on the users computer. Which should help simplify the setup, and mean that it is easier to for users to run a couple of demo's at the same time.

[rtelicak]

Are these all the variables this project uses? Lets list them all so we have a better idea what needs to be setup prior to running it.

[nhall-tink]

After review, as this is a one-time payment, the only thing the client needs is the Client Id & Secret to create a session with Tink Link.

We could potentially parameterise something like the Product information, as it's hard coded a the moment. Which would mean the demo could be quickly repurposed via the config file, instead of changing server values.

  destinations: [
    {
      accountNumber: env.process.BANK_ACCOUNT_NUMBER,
      type: env.process.PAYMENT_TYPE
      reference: env.process.REFERENCE
    },
  ],
  recipientName: env.process.RECIPIENT_NAME
  sourceMessage: env.process.SOURCE_MESSAGE
  remittanceInformation: {
    type: env.process.RM_INFO_TYPE
    value: env.process.RM_INFO_VALUE
  },

Let me know your thoughts

[rtelicak]

I was thinking about moving all existing env variables in to this new .env variables, not creating a new ones. If REACT_APP_TINK_LINK_PAYMENT_CLIENT_ID and TINK_LINK_PAYMENT_CLIENT_SECRET is the only two, lets merge this.

cc: @shuma

[nhall-tink]

@rtelicak thanks! I don't have merge perms still but happy to see this move forward!