Best way to implement input based validation on a router procedure

  changeUserAccessWithinAccount: protectedProcedure
    .input(z.object({ user_id: z.number(), account_id: z.number(), access: z.enum([ACCOUNT_ACCESS.ADMIN, ACCOUNT_ACCESS.OWNER, ACCOUNT_ACCESS.READ_ONLY, ACCOUNT_ACCESS.READ_WRITE]) }))
    .query(async ({ ctx, input }) => {
      // validate that the context user is an admin within the account specified as an input param.... where should this go.. an additional input parser?
      const test_membership = ctx.dbUser.memberships.find(membership => membership.account_id == input.account_id);
      if(!test_membership || (test_membership?.access !== ACCOUNT_ACCESS.ADMIN && test_membership?.access !== ACCOUNT_ACCESS.OWNER)) {
        throw new TRPCError({ code: 'UNAUTHORIZED' });
      }
      //....do the thing...