Add unit tests for shared user covering shared and separate database

[maliming]

Adds abstract test suites in TestBase and concrete EF/Mongo subclasses for shared user (IdentityUserManager.FindSharedUserBy*Async) under both shared-database and separate-database multi-tenancy topologies.

[Copilot]

Pull request overview

Adds reusable unit test suites to validate IdentityUserManager.FindSharedUserBy*Async behavior for shared-user mode across both shared database and separate database multi-tenancy topologies, with concrete EF Core and MongoDB runners.

Changes:

• Introduces abstract shared-user test suites in Volo.Abp.Identity.TestBase for shared DB and separate DB topologies.
• Adds concrete EF Core and MongoDB test classes/modules to execute the suites on each backend/topology.
• Removes the older inlined shared-user test class from IdentityUserManager_Tests.cs in favor of the new shared suites.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
modules/identity/test/Volo.Abp.Identity.TestBase/Volo/Abp/Identity/IdentityUserManager_SharedUser_Tests.cs	New abstract suite covering shared-user resolution (email/name/login/passkey/id) in shared-db mode.
modules/identity/test/Volo.Abp.Identity.TestBase/Volo/Abp/Identity/IdentityUserManager_SharedUser_SeparateDatabase_Tests.cs	New abstract suite verifying separate-database isolation semantics under shared-user mode.
modules/identity/test/Volo.Abp.Identity.MongoDB.Tests/Volo/Abp/Identity/MongoDB/IdentityUserManager_SharedUser_Tests.cs	MongoDB concrete runner for shared-db shared-user suite.
modules/identity/test/Volo.Abp.Identity.MongoDB.Tests/Volo/Abp/Identity/MongoDB/IdentityUserManager_SharedUser_SeparateDatabase_Tests.cs	MongoDB concrete runner for separate-db isolation suite.
modules/identity/test/Volo.Abp.Identity.MongoDB.Tests/Volo/Abp/Identity/MongoDB/AbpIdentitySharedUserSeparateDbMongoDbTestModule.cs	MongoDB test module configuring two predefined tenants with separate physical databases.
modules/identity/test/Volo.Abp.Identity.EntityFrameworkCore.Tests/Volo/Abp/Identity/EntityFrameworkCore/AbpIdentitySharedUserSeparateDbEntityFrameworkCoreTestModule.cs	EF Core test module configuring host + two tenants with separate in-memory SQLite databases.
modules/identity/test/Volo.Abp.Identity.Domain.Tests/Volo/Abp/Identity/IdentityUserManager_Tests.cs	Removes the previous dedicated shared-user test class now covered by the new suites.
modules/identity/test/Volo.Abp.Identity.Domain.Tests/Volo/Abp/Identity/IdentityUserManager_SharedUser_Tests.cs	EF-based concrete runner for shared-db shared-user suite.
modules/identity/test/Volo.Abp.Identity.Domain.Tests/Volo/Abp/Identity/IdentityUserManager_SharedUser_SeparateDatabase_Tests.cs	EF-based concrete runner for separate-db isolation suite.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated no new comments.