[FEATURE] Support multiple bank data provider

[DenuxPlays]

Is your feature request related to a problem? Please describe.

Currently it is not possible to add or support other providers then GoCardless which makes us extremely dependent on them.

Describe the solution you'd like

I like to implement the following:

• GoCardless (being done in: Sync bank data #443)
• Plaid
  • Make whole structure more extendable

This would create a foundation that makes it easier to implement other/more provider to make us more independent.

Disclaimer

This is the goal for the stable release and not a huge priority at the moment.