feat(LAB-02): add laboratory metadata model and tests - #43

Component and requirement IDs

• Component: Platform.LabMetadata
• Implemented requirement: LAB-02 (laboratory metadata)
• Dependency: LAB-01 (stable laboratory identity, owned by Team 14)
• Team: 20
• Author(s): Dragana Nikić

Changes

• Implemented the LaboratoryMetadata model containing LaboratoryId, objective, difficulty, type, and tags.
• Uses LaboratoryId (Guid) as a reference to the laboratory identity provided by LAB-01.
• Does not implement or replace the LAB-01 laboratory identity.
• Added LaboratoryDifficulty and LaboratoryType enums.
• Implemented validation of required fields and allowed enum values.
• Implemented tag normalization, including trimming, lowercase conversion, and removal of duplicates and empty tags.
• Updated the Platform.LabMetadata.Tests project with tests for metadata validation.
• Registered the metadata and test projects in SecurityLab.slnx.

Verification

• Solution build completed successfully with 0 errors.
• All 7 Platform.LabMetadata.Tests unit tests passed.
• GitHub CI checks passed for both backend and frontend.

Architecture and data flow

• LAB-02 metadata is implemented in a separate C# class library.
• Laboratory identity belongs to LAB-01 (Team 14).
• LaboratoryId is used only as a reference to that identity.
• No database or API integration is included in this change.

Security checks and negative tests

• Invalid difficulty and laboratory type values are rejected.
• Empty laboratory IDs and required metadata fields are rejected.
• Null tag collections are rejected.

Dependencies

• Targets .NET 10.
• Test project references Platform.LabMetadata and uses NUnit.
• Database, repository, and API integration are outside the scope of this change.