Feat: SimpleFin Integration

[Himmelschmidt]

Describe the feature

SimpleFin integration for accounts

Why is this feature important?

Currently the only option for third party syncing seems to be Plaid, which has a convoluted process to setup and approve an account.

Additional context, screenshots, and relevant links

I have a PR ready (PR #94) for it but want to open this up for discussion here.

[PrplHaz4]

Happy to see this here and think it goes a long way towards helping self-hosted adoption.

Benefits to SimpleFin over Plaid:

• No complex application process
• No need to expose webhook endpoint to internet (depending on implementation I'm guessing)
• Integrations available for multiple popular-ish apps (Firefly, Actual, Buckets, Ledger...)
• Predictable cost (although for most ppl pay-as-you-go Plaid likely comes out slightly cheaper)

Cons:

• Yet another (untrusted trending positive) 3rd Party (2 new parties if you count MX also)
• Mostly redundant with Plaid for US - maintenance burden of maintaining two sync providers
• Not as close-to-the-metal for DIYers/Privacy nerds