Add Couchbase EF Core Provider Integration

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

ABP Framework doesn't currently support Couchbase database, which is a popular enterprise NoSQL document database.

Describe the solution you'd like

Add a new package Volo.Abp.EntityFrameworkCore.Couchbase using the official Couchbase EF Core Provider (Couchbase.EntityFrameworkCore).

Following the same pattern as Volo.Abp.EntityFrameworkCore.PostgreSql:

• AbpEntityFrameworkCoreCouchbaseModule - Module registration
• UseCouchbase() extension methods for AbpDbContextOptions and AbpDbContextConfigurationContext
• CouchbaseConnectionStringChecker - Connection validation
• AbpCouchbaseModelBuilderExtensions - Model builder extension
• Add Couchbase to EfCoreDatabaseProvider enum

Additional context

• Provider: Couchbase EFCore Provider
• NuGet: Couchbase.EntityFrameworkCore
• Compatibility: EF Core 8.0+, .NET 8+, Couchbase Server 7.6+

I'm willing to implement this and submit a PR.

Start by examining the existing Volo.Abp.EntityFrameworkCore.PostgreSql package and its module, options extensions, connection string checker, model builder extensions, and EfCoreDatabaseProvider enum. Review the Couchbase EF Core Provider documentation and compatibility requirements before defining the new package. Done means the Couchbase provider integration exposes all requested components and supports the stated EF Core, .NET, and Couchbase versions.