feat: setup the invoice backend

apps/edr-freight-api/src/modules/billing/dto/pay-invoice.dto.ts

@@ -0,0 +1,30 @@
+import { ApiPropertyOptional } from "@nestjs/swagger";
+import { IsIn, IsOptional, IsString } from "class-validator";
+
+/** Gateway options for paying an invoice from the customer portal. */
+export class PayInvoiceDto {
+  @ApiPropertyOptional({ description: "Payment method (defaults to TELEBIRR)." })
+  @IsOptional()
+  @IsString()
+  method?: string;
+
+  @ApiPropertyOptional({ enum: ["web", "mobile"], default: "web" })
+  @IsOptional()
+  @IsIn(["web", "mobile"])
+  platform?: "web" | "mobile";
+
+  @ApiPropertyOptional({ description: "Payer account / phone, for wallet methods." })
+  @IsOptional()
+  @IsString()
+  payerAccount?: string;
+
+  @ApiPropertyOptional({ description: "Browser redirect URL on success." })
+  @IsOptional()
+  @IsString()
+  returnUrl?: string;
+
+  @ApiPropertyOptional({ description: "Browser redirect URL on failure." })
+  @IsOptional()
+  @IsString()
+  failureUrl?: string;
+}