Use strictly-typed result and error types [SDK-2977]

[Widcket]

Changes

⚠️ THIS PR CONTAINS BREAKING CHANGES

Currently, the Result type (aliased to Auth0Result) has the error typed as Error instead of the specific error type (e.g. WebAuthError, CredentialsManagerError, etc), so the error has to be casted, and the compiler cannot enforce that Web Auth only produces WebAuthError errors, and the Credentials Manager only produces CredentialsManagerError, and so on. This unnecessarily complicates the error handling and degrades the DX.

This PR replaces Auth0Result with more specific alternatives:

• AuthenticationResult<T> -> Result<T, AuthenticationError>
• ManagementResult<T> -> Result<T, ManagementError>
• WebAuthResult<T> -> Result<T, WebAuthError>
• CredentialsManagerResult<T> -> Result<T, CredentialsManagerError>

Additionally, the Credentials Manager was updated to use a Result type, like the rest of the library.

Testing

The Credentials Manager changes have been tested manually in test apps, by performing Web Auth login, saving the credentials, and then retrieving them, as follows:

Using Cocoapods

• iOS 15.0 (simulator)
• macOS 11.6.1
• macOS 11.6.1 Catalyst

Using Carthage

• iOS 15.0 (simulator)
• macOS 11.6.1
• macOS 11.6.1 Catalyst Carthage does not support building XCFrameworks for macCatalyst

Using SPM

• iOS 15.0 (simulator)
• macOS 11.6.1
• macOS 11.6.1 Catalyst

• This change adds unit test coverage
• This change has been tested on the latest version of the platform/language or why not

Checklist

• I have read the Auth0 general contribution guidelines
• All existing and new tests complete without errors
• All active GitHub checks have passed