Fix concurrency issues in Swift 6

[alexruperez]

Description:

With the upcoming Swift 6 release, strict concurrency checks will be enforced. Our project, SecurePropertyStorage, currently has several warnings related to concurrency safety that need to be addressed to ensure compatibility and stability. This issue aims to track and resolve all these warnings.

Steps to Reproduce:

1. Open SecurePropertyStorage.xcodeproj project file.
2. Set the SWIFT_STRICT_CONCURRENCY flag to complete in the project build settings.
3. Run SecurePropertyStorage-Package scheme tests.
4. Observe the warnings related to concurrency safety.

Warnings to Fix:

Associated Value Warnings:

1. InjectError enum warnings:
   • Location: Sources/Inject/InjectError.swift:4:10
     • Associated value notFound(_:qualifiers:group:) of Sendable-conforming enum InjectError has non-sendable type Any
     • Associated value notFound(_:qualifiers:group:) of Sendable-conforming enum InjectError has non-sendable type Qualifier (aka Protocol)
   • Location: Sources/Inject/InjectError.swift:6:10
     • Associated value moreThanOne(_:qualifiers:group:) of Sendable-conforming enum InjectError has non-sendable type Any
     • Associated value moreThanOne(_:qualifiers:group:) of Sendable-conforming enum InjectError has non-sendable type Qualifier (aka Protocol)

Static Property Warnings:

2. Static property 'shared' is not concurrency-safe:
   • Locations:
     • Sources/Inject/InjectStorage.swift:7:24
     • Sources/Keychain/KeychainStorage.swift:9:24
     • Sources/Singleton/SingletonStorage.swift:10:24
     • Sources/UserDefault/UserDefaultsStorage.swift:10:24

Test Warnings:

3. Static property 'allTests' is not concurrency-safe:

   • Locations:
     • Tests/SecurePropertyStorageTests/InjectTests.swift:195:16
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:252:16
     • Tests/SecurePropertyStorageTests/SingletonTests.swift:79:16
     • Tests/SecurePropertyStorageTests/UserDefaultTests.swift:243:16

4. Let properties not concurrency-safe:

   • Locations:
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:10:5
     • Tests/SecurePropertyStorageTests/SingletonTests.swift:10:5
     • Tests/SecurePropertyStorageTests/UserDefaultTests.swift:10:5

5. Call to main actor-isolated instance method waitForExpectations(timeout:handler:) in a synchronous nonisolated context:

   • Locations:
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:65:9
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:81:9
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:97:9
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:111:9
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:127:9
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:141:9
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:157:9
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:171:9
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:187:9
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:201:9
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:217:9
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:233:9
     • Tests/SecurePropertyStorageTests/KeychainTests.swift:249:9

Proposed Solution:

• Ensure all associated values in Sendable-conforming enums are of Sendable types.
• Modify static properties to conform to Sendable or isolate them to a global actor.
• Ensure all tests and shared mutable states are concurrency-safe or properly isolated.

References:

• Swift Concurrency
• Swift 6 Migration Guide
• Concurrency-safe global variables to prevent data races