Add customers management module with database schema and validation

- Introduced `CustomersModule` to manage customer data, including read and write controllers.
- Created database migrations for the `customers` and `customer_contacts` tables, including constraints and unique indexes.
- Implemented validation for customer fields such as name, code, and address with corresponding utility functions.
- Developed service and repository layers for handling customer data operations.
- Added unit tests for the customers service, repository, and controllers to ensure functionality and correctness.
- Updated application module to include the new `CustomersModule` for better organization.

src/modules/configuration/configuration.module.ts

@@ -1,9 +1,10 @@
 import { Module } from '@nestjs/common';
 import { BranchesModule } from './branches/branches.module';
+import { CustomersModule } from './customers/customers.module';
 import { DivisionsModule } from './divisions/divisions.module';
 
 @Module({
-  imports: [DivisionsModule, BranchesModule],
-  exports: [DivisionsModule, BranchesModule],
+  imports: [DivisionsModule, BranchesModule, CustomersModule],
+  exports: [DivisionsModule, BranchesModule, CustomersModule],
 })
 export class ConfigurationModule {}