Hash Opal Tokens in the database

[GeekInTheNorth]

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[Copilot]

Pull Request Overview

This PR implements secure token hashing for Opal tokens in the database using PBKDF2 with SHA256. Previously, tokens were stored in plain text, which posed a significant security risk.

• Introduces a token hashing service using PBKDF2-SHA256 with 100,000 iterations
• Replaces plain text token storage with hashed tokens and display tokens
• Updates authentication flow to verify tokens against hashes instead of plain text comparison

Reviewed Changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
TokenModel.cs	Adds CreatedDate property for salt generation
TokenHashService.cs	New service implementing secure PBKDF2 token hashing
ITokenHashService.cs	Interface for token hashing operations
OpalTokenEntity.cs	Replaces Token field with TokenHash, DisplayToken, and TokenSalt fields
OpalTokenRepository.cs	Updates to hash tokens on save and verify via GetByToken method
OpalTokenController.cs	Adds validation and error handling improvements
OpalAuthorizationAttribute.cs	Updates to use GetByToken method for hash-based verification
RobotsServiceExtensions.cs	Registers TokenHashService in DI container
TokenHashServiceTests.cs	Comprehensive unit tests for hashing service
OpalTokenControllerTests.cs	Removes obsolete token obfuscation tests
OpalAuthorizationAttributeTests.cs	Updates tests to work with new hashing approach

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