Replace mediatr with cortext.mediator

[Carl Sixsmith (carlsixsmith-moj)]

🔗 Related Work

• Closes: # https://dsdmoj.atlassian.net/browse/CFODEV-1172
• Related: #

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📌 Summary

Replaces the MediatR package with Cortex.Mediator.

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🎯 Purpose / Motivation

Why does this change exist? What problem are we solving?

MediatR moved away from open source to a paid subscriber model.

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🧠 Approach

Queries and Commands are now split for dedicated interfaces

🧪 How to Test

Step-by-step instructions to verify this works.

Requires a full system regression test.

⚠️ Risks & Impact

• Breaking change
• Database change
• Performance impact
• Security impact

Details:

Anything reviewers should be cautious about.

This is a massive change and should not be merged until we are fully confident all issues are ironed out.

🙋 Notes for Reviewers

This pull request migrates the application from using MediatR to Cortex.Mediator as the in-process messaging library, updating dependencies, interfaces, and documentation accordingly. It also removes MediatR-specific exception handlers and introduces new compatibility and mediator infrastructure to support Cortex.Mediator. The changes affect package references, architectural documentation, key interfaces, and the dependency injection setup.

Migration from MediatR to Cortex.Mediator:

• Replaces the MediatR NuGet package with Cortex.Mediator in the solution's dependencies and removes MediatR from Renovate configuration. (Directory.Packages.props [1] src/Application/Application.csproj [2] renovate.json [3]
• Updates Clean Architecture documentation and code samples to reference Cortex.Mediator and its types (ICommand<T>, IQuery<T>, etc.) instead of MediatR (IRequest<T>). (.github/copilot-instructions.md [1] [2] [3] [4]
• Changes the pipeline behaviors and validation constants to use Cortex.Mediator terminology. (.github/copilot-instructions.md [1] src/Application/Common/Validators/ValidationConstants.cs [2]

Codebase and Interface Refactoring:

• Updates core interfaces to use Cortex.Mediator types:
  • ICacheInvalidatorRequest<TResponse> now inherits from ICommand<TResponse> instead of IRequest<TResponse>. (src/Application/Common/Interfaces/Caching/ICacheInvalidatorRequest.cs src/Application/Common/Interfaces/Caching/ICacheInvalidatorRequest.csL3-R3)
  • ICacheableRequest<TResponse> now inherits from IQuery<TResponse>. (src/Application/Common/Interfaces/Caching/ICacheableRequest.cs src/Application/Common/Interfaces/Caching/ICacheableRequest.csL3-R3)
  • IAuditableRequest<TResponse> now inherits from IQuery<TResponse>. (src/Application/Common/Interfaces/IAuditableRequest.cs src/Application/Common/Interfaces/IAuditableRequest.csL4-L8)
  • Updates message bus ICommand documentation to clarify distinction from mediator commands. (src/Application/Common/MessageBus/ICommand.cs src/Application/Common/MessageBus/ICommand.csL6-R6)
• Refactors features (e.g., AbandonActivity) to use Cortex.Mediator command and handler types. (src/Application/Features/Activities/Commands/AbandonActivity.cs [1] [2]

Mediator Infrastructure and Compatibility:

• Adds SequentialNotificationMediator to ensure notifications are handled sequentially and integrates it as the application's mediator implementation. (src/Application/Common/Mediator/SequentialNotificationMediator.cs [1] src/Application/DependencyInjection.cs [2] [3]
• Introduces MediatorCompatibilityExtensions to provide MediatR-like extension methods for Cortex.Mediator, aiding migration and compatibility. (src/Application/Common/Extensions/MediatorCompatibilityExtensions.cs src/Application/Common/Extensions/MediatorCompatibilityExtensions.csR1-R38)

Dependency Injection and Pipeline Behaviors:

• Updates dependency injection to register Cortex.Mediator and its pipeline behaviors, replacing MediatR registrations. (src/Application/DependencyInjection.cs src/Application/DependencyInjection.csR14-R45)

Cleanup of MediatR-specific Exception Handlers:

• Removes MediatR-specific exception handler classes (DbExceptionHandler, ServerExceptionHandler, ValidationExceptionHandler). (src/Application/Common/Exceptions/DbExceptionHandler.cs [1] src/Application/Common/Exceptions/ServerExceptionHandler.cs [2] src/Application/Common/Exceptions/ValidationExceptionHandler.cs [3]

[Copilot]

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[Carl Sixsmith (carlsixsmith-moj)]

Tested:

• Searches
• Document Exports
• Payments
• QA