const getParams = (id: number) => ({
  where: {id},
  select: {id: true, otherCustomers: { select: { id: true, otherCustomers: true } }}
})

ctx.log.debug('init customerTree')
const baseCustomer = await ctx.prisma.customer.findUnique(getParams(args.id))
if(!baseCustomer) return null

const customers: any[] = []

type TraverseCustomer = CustomerType & { customer: CustomerType | null; otherCustomers: TraverseCustomer[]; }
async function traverse(node: TraverseCustomer) {
  node?.otherCustomers.forEach(customer => {
    customers.push(customer)
    if(customer.otherCustomers) {
      const subCustomer = await ctx.prisma.customer.findUnique(getParams(customer.id))
      ctx.log.debug(JSON.stringify(subCustomer, null, 2))
      traverse(subCustomer)
    }
  })
}
traverse(baseCustomer)

subCustomers