[Auth Service] Add test coverage for new database functions in CQRS implementation

[coderabbitai]

Background

In PR #4512, we introduced CQRS pattern support with dual database connections in the Auth Service. CodeRabbit identified that several of the new database functions lack test coverage.

Required Action

Add thorough tests for the following new database functions:

• getCommandTenantDB
• getQueryTenantDB
• getCommandModelByTenant
• getQueryModelByTenant

Importance

Since database operations are critical to the application, these functions must be comprehensively covered with tests that validate both successful paths (e.g., correct database connection and model registration) and failure conditions (e.g., when a connection is not established).

References

• PR: [Auth Service] Add CQRS pattern support with dual database connections #4512
• Comment: [Auth Service] Add CQRS pattern support with dual database connections #4512 (comment)

Requested by

@Baalmart