Implement "infinite scroll" for expenses (#95)

* Extract ExpenseCard vom ExpenseList

* Implement simple pagination of expenses (see #30)

- display only this year's entries by default
- a "Show more" button reveals all expenses

* Turn getPrisma() into constant "prisma"

- getPrisma() is not async and doesn't need to be awaited
- turn getPrisma() into exported constant "prisma"

* Select fields to be returned by getGroupExpenses()

- make JSON more concise and less redundant
- some properties were removed (i.e.instead of "expense.paidById" use "expense.paidBy.id")

* Remove "participants" from ExpenseCard

- no need to search for participant by id to get it's name
- name property is already present in expense

* Add option to fetch a slice of group expenses

- specify offset and length to get expenses for [offset, offset+length[
- add function to get total number of group expenses

* Add api route for client to fetch group expenses

* Remove "Show more" button from expense list

* Implement infinite scroll

- in server component Page
  - only load first 200 expenses max
  - pass preloaded expenses and total count

- in client component ExpenseList, if there are more expenses to show
  - test if there are more expenses
  - append preloading "skeletons" to end of list
  - fetch more expenses when last item in list comes into view
  - after each fetch increase fetch-length by factor 1.5
    - rationale: db fetch usually is not the issue here, the longer the list gets, the longer react needs to redraw

* Use server action instead of api endpoint

* Fixes

---------

Co-authored-by: Sebastien Castiel <sebastien@castiel.me>

src/scripts/migrate.ts

@@ -1,6 +1,6 @@
 // @ts-nocheck
 import { randomId } from '@/lib/api'
-import { getPrisma } from '@/lib/prisma'
+import { prisma } from '@/lib/prisma'
 import { Prisma } from '@prisma/client'
 import { Client } from 'pg'
 
@@ -8,8 +8,6 @@ process.env.NODE_TLS_REJECT_UNAUTHORIZED = '0'
 
 async function main() {
   withClient(async (client) => {
-    const prisma = await getPrisma()
-
     // console.log('Deleting all groups…')
     // await prisma.group.deleteMany({})