feat: ZapPlanner custom app

[rolznz]

TODOs:

• add card on home page if the user has no zapplanner apps
• ability to provide an optional name and message through dialog
• create subscription via api and save subscription ID to the app metadata
• change to sat pricing, not fiat
• review method of app detail page interacting with zapplanner (should this be proxied through alby hub rather than adding a CSRF exception?)

[bumi]

that's super cool!

can we add a quick note somewhere explaining on how it works?

"ZapPlanner is a tool to securely schedule recurring payments. A new special app connection with a strict budget is created for each scheduled payment. This allows you to securely setup recurring payments and be in full control"

[rolznz]

@bumi @reneaaron I will merge it as is for now.

I am not really happy with the CSRF exception here, but I discussed with Rene and this was a way to do a quick proof of concept. The other option is to proxy the API calls through the backend, but this requires some thought architecturally as it means an app detail page also requires adding routes, and then is much more complicated and possibly more in the direction of proper plugins.